Too often, security programs significantly slow down the computer, causing lags in booting up the machine, launching programs and receiving email. Not only that, they can be incredibly annoying, popping up frequent messages or asking questions in techie lingo.

The main screen of the 2009 version of Norton Internet Security is streamlined and even includes a gauge to show much drain the security program is placing on the computer.

Now, Symantec (SYMC) has decided to radically rewrite its main security suite for Windows to directly address these problems. And in my tests, this new product, Norton Internet Security 2009, largely succeeded. It isn’t perfect, but it is the fastest, simplest and least obtrusive security suite I have ever used.

Being quick and quiet is great, but, of course, a security product also has to be effective against the vast number of viruses, spyware programs and other malicious attacks aimed at Windows. I don’t have a security lab in which to test such effectiveness. But PC Magazine does, and the magazine called the new Norton suite’s spyware and virus protection “extremely effective.” The magazine’s tests are described at http://www.pcmag.com/article2/0,2817,2330024,00.asp.

However, I wasn’t impressed with Norton’s optional antispam feature, which caused the only significant problem I ran into in my testing.

The new suite costs $70, and can be purchased at symantec.com and elsewhere. For that price, you get to install it on three PCs and you get a one-year subscription to its updates, which cost $60 thereafter.

Symantec is now including free support, even over the phone, though in my tests this support proved lousy. Norton Internet Security 2009 works only on Windows XP and Windows Vista.

I tested the new security suite on a Dell (DELL) desktop running Vista and on a Macintosh laptop running Windows XP as a “virtual machine,” meaning Windows and Windows programs ran simultaneously with the Mac operating system. Symantec assured me the program would run properly in this latter setup, and I had run the previous version of Norton successfully in the same environment.

The first thing you notice about NIS 2009 is the fast and simple installation. The process took under two minutes on each of my test machines.

File scanning is also much faster, partly because the new suite has a feature called Insight that allows it to skip the scanning and rescanning of many of your files. Insight gathers information about your installed programs and compares them against a list of programs Symantec knows are “trusted,” through either its own research or through scanning results voluntarily submitted by other users. These trusted programs are then exempted from future scans, saving a ton of time.

The new Norton suite has a feature called Insight which calculates how many of your programs it knows are trusted, and therefore needn’t be scanned repeatedly, saving time.

For instance, on my Dell running Vista, an immediate complete scan done before Insight analyzed the computer took more than an hour. But after Insight determined that over 70% of my programs were trusted, complete scans took 10 minutes or less. Of course, your data files, like Word documents and emails, still must be scanned, because they are typically unique.

To minimize the impact on users, the new Norton does scanning and other tasks only when it detects that the computer has been idle for at least 10 minutes. And new virus definitions trickle into your computer invisibly, in the background, rather than all at once in a major process.

Symantec is so certain that its product has a low impact on PC performance that it built a gauge into its new streamlined main screen that shows its drain on the main processor, or CPU.

NIS 2009 is also far less annoying than other suites I’ve used. In normal operation, it notifies you only when it has completed a background task or if there’s a threat or a repair that requires a user action, such as a reboot. And there’s an even quieter optional “silent mode” that can turn off nearly every nonurgent activity of Norton for up to six hours. Silent Mode is automatically activated during full-screen activities, such as playing games or watching movies.

The new suite has a bunch of other features, including a browser toolbar for Internet Explorer and Firefox that warns against fake and malicious Web pages, and that can securely enter your passwords and other information on Web sites. It also has an antispam feature for Microsoft (MSFT) Outlook and Outlook Express.

This antispam feature, which is off by default, was rated as weak by PC Magazine and, in my tests, it caused both Norton and Outlook Express to crash repeatedly in Windows XP running on my Mac. Symantec suspects this is a problem particular to running Windows the way I was on the Mac. After I reinstalled Norton and turned off the feature, all was well again.

But Symantec’s free tech-support service was not only unable to diagnose the problem, it didn’t even know the difference between Outlook and Outlook Express.

Despite this one glitch, I can recommend Norton Internet Security 2009 as a good way to protect your Windows computer with minimal impact on your time and attention.

Find all of Walt Mossberg’s columns and videos online, free, at the All Things Digital Web site, walt.allthingsd.com. Email him at mossberg@wsj.com.

But just how good is Chrome? How does it differ from IE and from less popular, but still important, browsers like Mozilla’s Firefox and Apple’s Safari?

I’ve been testing Chrome for about a week, trying out all its features and using it side by side with Microsoft’s latest iteration of IE, which came out just last week.

My verdict: Chrome is a smart, innovative browser that, in many common scenarios, will make using the Web faster, easier and less frustrating. But this first version — which is just a beta, or test, release — is rough around the edges and lacks some common browser features Google plans to add later. These omissions include a way to manage bookmarks, a command for emailing links and pages directly from the browser, and even a progress bar to show how much of a Web page has loaded.

Chrome’s interface has some bold changes from the standard browser design. These new features enhance the Web experience, but they will require some adjustment on the part of users. For instance, Chrome does away with most menus and toolbar icons to give maximum screen space for the Web pages themselves. Also, Google has merged the address bar, where you type in Web addresses, with the search box, where you type in search terms. This unified feature is called the Omnibox.

One striking difference in Chrome is how it handles tabs, which display a single Web page. In Chrome, each tab behaves as a separate browser. The bookmarks bar, Omnibox, menus and toolbar icons are located inside the tab, rather than atop the entire browser. The tabs appear at the top of the computer screen. Chrome also groups related tabs. If you open a new tab from a link in a page that’s already open, that new tab appears next to the originating page, rather than at the end of the row of tabs.

Despite Google’s claims that Chrome is fast, it was notably slower in my tests at the common task of launching Web pages than either Firefox or Safari. However, it proved faster than the latest version of IE — also a beta version — called IE8.

Meanwhile, Microsoft hasn’t been sitting still. The second beta version of IE8 is the best edition of Internet Explorer in years. It is packed with new features of its own, some of which are similar to those in Chrome, and some of which, in my view, top Chrome’s features.

Google’s Chrome browser displays thumbnails of a user’s most-visited pages when a new tab is opened, rather than a blank page.

For example, while IE8 also groups related tabs, it assigns a different color to each such tab group and allows you to close them all with one click. It has a “smart” address box of its own, that drops down a list of suggestions as you type, though it retains a separate search box.

IE8 also has breakthrough privacy features that exceed Chrome’s, and includes a new technology called Accelerators, which allows you to take rapid action on any selected word or phrase on a Web page, such as generating a map for a place name, without switching to a new page.

As they develop, each of these browsers has a good chance of besting Firefox 3.0, which I have regarded as the best Web browser for Windows, the only operating system on which Chrome currently runs. But they will have to get faster at loading pages. And, to best Firefox on the Macintosh, Google will have to make good on its promise to produce a Mac version of Chrome, something it says it will do in the coming months. Microsoft has no plans to produce a Mac version of IE8.

Chrome and IE8 are far more advanced than Apple’s Safari. Safari is speedy on both Mac and Windows platforms, but lacks many of the key intelligent features of its newer Google and Microsoft rivals.

Why is Google igniting a new browser war? There are two main reasons, and both involve competing with Microsoft. First, the search giant fears that because its search engine and other major products depend on the browser, Microsoft — with its rival online products — might be able to gain an advantage by altering the design of IE, which has roughly a 75% market share.

Second, and more important, Google sees the Web as a platform for the software programs, or applications, that currently run directly on computer operating systems, notably Microsoft’s Windows. It says current browsers lack the underlying architecture to enable future, more powerful Web applications that will rely more heavily on a common Web programming language called JavaScript. Chrome was designed to be the world’s speediest browser at handling JavaScript.

That move might one day make Chrome a sort of online operating system that competes with Windows. “Think of Chrome as more than a simple Web browser,” Google declares. “It’s a platform for running Web applications.”

Microsoft’s IE8 has an “Accelerator” feature that lets users select any Web text and then map, translate, search or email their selection without leaving the page.

I tested Chrome, and IE8, on a plain-vanilla Lenovo ThinkPad laptop running Windows XP, and equipped with a modest processor and one gigabyte of memory.

To gauge Chrome’s speed at loading Web pages, I launched two large groups of typical Web pages simultaneously, each site opening in its own tab. One group included 15 sports sites, the second 19 news sites. In both tests, Chrome’s speed fell in the middle, at 35 and 44 seconds, respectively. IE8 was slower, taking 49 and 75 seconds to open the two groups of sites. But Firefox and Safari were much faster, notching identical speeds of 19 seconds for the 15 sites and 28 seconds for the 19 sites.

Google claims that future, more sophisticated Web applications relying more heavily on JavaScript than today’s sites do would run faster on Chrome. Of course, I couldn’t test any claim about future scenarios, but I did run Chrome on several JavaScript test sites, used by developers. It handily beat the other browsers. However, Google doesn’t claim users would see much difference on current Web application sites.

I also tested Chrome’s compatibility with scores of common Web sites. In general, it did well, rendering the sites properly. But I ran into problems with video. Some video sites refused to recognize Chrome, because its development has been a secret. On others, like Major League Baseball’s site, videos mostly played properly, but sometimes didn’t.

IE8 also has some compatibility issues, for different reasons. It’s the first version of Internet Explorer to hew closely to Web standards. Earlier versions used some nonstandard ways of rendering Web sites, prompting some site designers to adopt techniques that made their pages work in IE, but look odd in Firefox and Safari. Now, ironically, these pages also look strange in IE8. So Microsoft was forced to build in a special Compatibility View button that users must click to see the sites properly.

Chrome is built on three core design principles. The first is its spare user interface: just two menus and a handful of toolbar icons. IE introduced a similar approach in its version 7, but with a difference. Microsoft allows users to restore a traditional menu bar; Google doesn’t. The only toolbar icon you can add in Chrome is a Home button.

The second principle is that a user can type anything into a single place, the Omnibox, and instantly get suggestions on where to go, gleaned from the user’s own browsing history and Google’s rankings of popular sites. Whether you type in a Web address or a search term, the Omnibox is very smart. In my tests, it sometimes came up with the right destination after I typed only one or two letters of the name of a site I often visited.

The Omnibox has another cool feature: Tab-to-Search. If you type in the name of another site that includes its own search feature, like Amazon.com, the Omnibox lets you just press the tab key to search within that site, without opening it first. Chrome, through its Options settings, also lets you change the default search engine used by the Omnibox. Instead of Google’s own search service, you can use Microsoft’s Live search, Yahoo search, or others.

The third big principle behind Chrome is that each tab runs, under the hood, as a separate browser. Tabs can be dragged off the main browser and turned into separate windows. If one tab crashes, the rest of the browser keeps running. But this doesn’t work perfectly. In my tests, all of Chrome died on me when I tried watching an Olympics video on the NBC site.

You can even make a tab a standalone application that runs from the Start Menu, or the desktop, as if it was a separate program.

Chrome has a few other key features. When you open a new tab, you don’t get a blank page, but a set of thumbnails for your most-visited pages, plus lists of recent search engines you’ve used, recently used bookmarks and recently closed tabs.

Like other browsers, Chrome puts up a warning when you try to visit a malicious or phony Web site, and it has a private browsing mode, called Incognito, which allows you to browse without leaving any history on your computer — a feature popularized in Safari.

Chrome also has a pop-up blocker, but it’s annoying because it flashes a notice that a pop-up has been blocked. IE also does this, but unlike in Chrome, the warnings are much less intrusive.

Internet Explorer 8 has some new features Chrome lacks. Its private browsing mode, called InPrivate, is the first I’ve seen that not only leaves no traces on your own computer, but also bars Web sites from collecting some types of information on where you’ve previously been surfing.

While IE8’s address box and search box remain separate, each also offers rapid suggestions; and both are organized better than Chrome’s. For instance, the suggestions that drop down from its address bar are divided neatly into categories drawn from the browser’s own guess, your history and your favorites. One downside: For this to work in Windows XP, you must first install Microsoft’s desktop search product.

Like Chrome, IE8 lets you switch your default search provider, but it also allows you to switch search engines on the fly. When you type in a search term, icons for alternate search engines appear at the bottom of the suggestion list, and you need only click on these to see search results from, say, Google, instead of Microsoft’s own Live search engine.

IE8’s Accelerators feature presents a blue-arrow icon above any text on a Web page that you have selected. Clicking on the icon brings up a list of actions you can take using the selected text, such as posting it to a blog, emailing it, mapping it or searching it. While these actions are set by default to use Microsoft’s own Web services, you can change them to use Google’s, Yahoo’s, or those from other companies.

Microsoft also has built in a feature called Web Slices. These are portions of a Web site that a site developer can designate to appear in the IE8 Favorites bar and to constantly update themselves. An example might be bidding on eBay.

Like Chrome, IE8 also displays useful information whenever you create a new tab, including a list of recently closed tabs and a list of Accelerators.

With the emergence of Chrome, consumers have a new and innovative browser choice, and with IE8, the new browser war is sure to be a worthy contest.

Find all of Walt Mossberg’s columns and videos online, free, at the All Things Digital Web site, walt.allthingsd.com. Email him at mossberg@wsj.com.

This contrast has appeared sharper in recent years, as Microsoft’s Windows Vista operating system received a tepid critical response compared with Apple’s Leopard platform and as the company’s Live Web search service has slipped further behind Google’s. In addition, Microsoft’s cellphone software, Windows Mobile, looks old and creaky compared with Apple’s sleek iPhone and Google’s forthcoming Android mobile operating system.

But innovation does exist at Microsoft’s sprawling Redmond, Wash., campus. For instance, last year’s daring and radical redesign of Microsoft Office has been a critical and commercial success.

Now, there’s a sort of guerrilla team inside Microsoft designed to churn out innovative products more often and more rapidly. Called Live Labs, the unit is a small operation that aims to turn technology theories into real, Web-based products relatively quickly. It has only about 125 employees, and even that modest number is broken up into smaller teams tackling specific projects.

This week, Microsoft Live Labs is releasing its first broad consumer Web service, called Photosynth. This service turns multiple photos of a scene or site — say, an art gallery or a building — into a 3-D scene you can virtually “walk” through on the Web.

Unlike a simple 2-D panorama, which many photo programs can create from several pictures, a Photosynth creation, called a “synth,” is a virtual 3-D environment. It gives you the feeling you are in the middle of a room looking around, or circumnavigating a building or object. You can travel through a scene both laterally and vertically, and zoom in to see detailed, higher-resolution views of objects inside the synth, such as paintings on a wall.

For instance, you don’t just see a long, flat picture of Stonehenge or the Grand Canal in Venice. You are made to feel you are there, moving through these places, looking up at the sky or down at the ground, and pausing to examine more closely a particular stone, boat or building.

Such 3-D walk-through images have been around for awhile; they are used on some real-estate Web sites, for example, to show houses virtually. But Photosynth allows anyone to create them using any standard digital camera, and even using pictures you already possess that weren’t created with Photosynth in mind. You could even use photos of the same site taken by several people. The software will analyze the pictures, figure out which ones overlap and in what order, and then turn those shots that match up into a 3-D synth.

Photosynth, based on technology Microsoft acquired in 2006, is entirely free, and it’s entirely based on the Web, at photosynth.net (where it will be launched at midnight EST Thursday). At that site you can view not only your own synths, but the synths created by every other Photosynth user.

I’ve been testing this service for about a week, and while it has its flaws, I believe that Photosynth offers a dramatic new way to use your photos and to share them with others.

Photosynth works within a Web browser, using a small plug-in you install. Currently, it works only in Windows, using Microsoft’s own Internet Explorer browser or its rival, Firefox. A Macintosh version is in the works, but for now, you can’t even view others’ synths in the Mac operating system.

When Photosynth works right, the results are wonderfully satisfying. But it takes some skill to get a set of photos the service can match up well, a quality Microsoft calls being “synthy.” Ideally, portions of each slice of a 3-D scene should show up in at least three photos, with 50% overlap between them. After you upload your pictures and Photosynth does its best to make them into a 3-D scene, the service assigns them a percentage number that indicates how synthy they were.

In my tests, I tried both collections of photos I already possessed and some I snapped with Photosynth in mind. My pictures of a piazza in Verona, Italy, were only 38% synthy, while ones I took of a hotel room specifically for Photosynth use were 73% synthy.

One gripe I had was that Photosynth doesn’t tell you how synthy your pictures are until after you have uploaded them and waited until the system merges them, a process that can take a long time over a slow Internet connection. It would be much better if the service could tell you in advance how synthy the pictures are. Another objection is that Photosynth has no privacy settings. All your synths are open to viewing by everyone who uses the service.

But, overall, Photosynth is an impressive new way to view and share photos, and an encouraging sign that innovation and creativity still live in Redmond.

Find all of Walt Mossberg’s columns and videos online, free, at the All Things Digital Web site, walt.allthingsd.com. Email him at mossberg@wsj.com.