Back in January, when I reviewed the massive new operating system, which took more than five years to develop, I called it “unexciting” because many of the breakthrough features Microsoft had planned for it had been jettisoned, and most of the rest were already present in the rival Apple Macintosh operating system, OS X.

But I also said it was “worthy,” and better than prior versions of Windows, because it has a stronger security system under the hood and better integrated searching.

Over the ensuing months, however, Vista has proved to be a disappointment, even though Microsoft says it’s selling like hotcakes. Based on my own experience and on reports from readers, it’s clear that many Vista PCs start up more slowly than new PCs running its predecessor, Windows XP, or than even well-worn Macs. And there is still a significant compatibility problem: Too many software and hardware products still don’t run, or don’t run properly, with Vista.

So, if you’re shopping for a new Windows computer, one of your first decisions is whether you want to get Vista, which comes on almost all new models, or to stick with Windows XP. PC makers are still offering XP on a few new consumer PCs. For instance, Dell offers four consumer laptops and two consumer desktops that can be ordered with XP.

Buying XP will likely result in fewer frustrations in the short run. But buying Vista may be the better choice for the long run. Over time, more and more products will be released that are tailored to the new system.

Your other option is to shun the Windows dilemma and buy a Macintosh. I regard the Mac operating system as superior to Windows, and Apple embeds it in beautifully designed machines. Macs have been spared the plague of viruses and spyware that afflicts Windows, and have better built-in multimedia software.

But, if you’re thinking of buying a Mac, it makes sense to wait a few weeks or months to gauge the early reviews and user reactions to Apple’s own new version of its operating system, called Leopard, due out Oct. 26. After that date, Apple won’t build in the current version of OS X, called Tiger, on new machines.

Here are some tips if you’re shopping for a new Windows PC this fall. They apply to desktop PCs and to most mainstream laptops, though there are additional considerations, such as size and weight and battery life, for smaller laptops meant primarily for travel. As always, these recommendations are intended for average consumers doing average tasks, not for heavy gamers, video professionals, or corporate buyers.

Operating system: If you opt for Vista, the best choice for average consumers is a version called Home Premium, which includes all of the new graphics and multimedia features. Many low-end PCs have only a stripped-down version called Home Basic. Some people may need Vista Business, a version that can link to some kinds of corporate networks that the two Home varieties can’t. If your budget allows, you can get an expensive version called Ultimate that includes the features of both the Home and Business versions.

Junk software: Most Windows consumer models are stuffed with “craplets” — crippled trial versions of programs. They take up space and can slow down the machine. One way to avoid these is to buy a so-called business PC, like one of Dell’s new Vostro models. Dell also allows you to opt out of trial software, especially when ordering its pricier XPS models. Many other manufacturers make this hard or impossible, especially if you buy a PC at a retail store. But the stores may clean up a new PC for a fee.

Memory: Buy at least one gigabyte of memory for Home Basic and at least two gigabytes for all other Vista versions.

Video: Vista’s flashy graphical interface works best with a separate, or “discrete,” graphics card that has its own memory. Some “integrated” graphics systems work fine, too, but they claim some of your main memory via an approach called shared memory.

Processor: Any “dual-core” processor from Intel or AMD should be fine for Vista. Don’t worry about processor speed. Buying added memory does more for performance.

Hard drive: Don’t scrimp on storage space, unless you are absolutely certain you won’t be saving many photos, songs or videos. Even an average PC should come with 300 gigabytes of hard-disk space for a reasonable price.

Performance: If you’re shopping in a retail store, try to check the performance rating Microsoft builds into Vista. It’s available by clicking “Show more details” in Vista’s “Welcome Center” screen. If this rating is below 3.0 on a Home Premium model, avoid the computer. For best results, shoot for 3.5 or higher.

Price: You can get a bargain-basement computer for under $400. But, for a versatile Vista PC with Home Premium, two gigabytes of memory, discrete video, a large hard disk and a dual-core processor, you should expect to spend $800 or more.

Email me at mossberg@wsj.com. Find all my columns and videos online free at the new All Things Digital web site, http://walt.allthingsd.com.

Dell has been having a tough time lately. Once the widely admired leader among PC makers, it has lost its sales crown to Hewlett-Packard and has seen its once-legendary customer satisfaction plunge.

In an attempt to jazz up its image, the stodgy behemoth recently introduced a line of thin, sleek, colorful consumer notebooks, the XPS M1330 series, but has been unable to build the machines on schedule.

Now, Dell is making another interesting move to better address the market. It has introduced a new sub-brand of computers intended for perhaps the most poorly served segment of computer buyers: really small businesses with 25 employees or less that have no full-time IT departments.

The new Dell line for these very small businesses is called Vostro. It fits into a new Dell brand lineup. All Dell’s consumer models, both laptop and desktop, are called Inspirons, a name formerly reserved only for laptops. Big business models are still called Latitude, Optiplex or Precison. High-performance consumer models are called XPS.

I’ve been testing a midrange Vostro model, a laptop with a 15.4-inch screen called the Vostro 1500. It’s a bulky, plain machine with nothing built in that Dell doesn’t already offer on consumer models, and some omissions that could make for extra setup work for small businesses. But it is fairly affordable and, to Dell’s credit, it comes without the useless trial software Dell and others cram onto consumer PCs.

Judged by its hardware and software, the Vostro 1500 is mostly a branding-and-marketing ploy at the moment. Dell concedes the new line is “just a first step” in what it swears will be a major initiative to serve very small businesses.

The only real small-business innovation lies outside the product itself: a dedicated phone support staff that Dell says has been trained specifically to serve these small companies. But unless you pay extra, you’ll still be dealing with support people based outside the U.S. — in Canada and in the Philippines, far from Dell’s Texas headquarters. Only time will tell if these folks can really provide better-than-usual service.

The Vostro 1500 starts at just $549, but that base model has very little memory and a small hard disk. The configuration Dell lent me for testing, with a decent two gigabytes of memory and a 160-gigabyte hard disk, plus an extra-large battery and a built-in Sprint cellular modem, costs $1,701. Dell says it’s available today at a promotional price of $1,327. The optional Sprint service requires a monthly fee, usually $60.

There are three other Vostro laptop models, including a very basic design called the Vostro 1000 that starts at just $449. Dell also offers Vostro desktops.

The Vostro 1500 I tested came with Windows XP instead of Windows Vista. Most Vostro models can be ordered with XP, which may be a welcome choice for small businesses that don’t want to wrestle with the continuing lack of compatible software and hardware for Vista.

Dell touts several features that it builds into the Vostro machines. One is a network setup program called Network Assistant. Another is PC Tuneup, which is maintenance software. A third is an online backup service that stores up to 10 gigabytes of data.

These are all useful, but none is new or tailored to small businesses. All were already available for Dell’s consumer models, albeit for small fees. Even the choice of Windows XP and the option to order a computer without any trial software have been available on some Dell consumer models.

Still, there were some surprising omissions on the Vostro that I tested. There was no security software, not even the usual 90-day subscription. Dell notes that you can opt to get the 90-day subscription free of charge and buy a 15-month security package for $79. It figures that many small businesses might already have access to security software. But because this is a necessity, installing it after the fact could be a hassle.

The Vostros with XP, like my test unit, also lack a modern, secure Web browser. They come with the old, insecure Internet Explorer 6.0 instead of Mozilla’s Firefox or Microsoft’s much safer Internet Explorer 7.0. A small business buying a Vostro with XP would have to immediately replace the browser.

And the Vostro doesn’t come bundled with any small-business software.

In my tests, the Vostro 1500 performed just fine, running quickly and easily connecting to my Wi-Fi network. But it’s a heavy, thick box that would be a burden for travelers. My configuration tipped the scales at seven pounds.

Yet, the battery life was only fair for such a bulky laptop, even with the extra-large battery. In my harsh battery test, where I turn off all power-saving software and play a loop of music, the Vostro 1500 lasted three hours and 36 minutes, meaning you’d likely get five hours, at most, in normal use. The standard battery would get you about a third less power.

Overall, the Vostro 1500 is just an OK laptop, which isn’t different enough from consumer models to really earn the small-business designation it claims.

Email me at mossberg@wsj.com. Find all my columns and videos online free at the new All Things Digital web site, http://walt.allthingsd.com.

Corrections & Amplifications:

Dell Inc. has introduced a computer line named Vostro for users at very small businesses. An earlier version of a headline on this column incorrectly said the line was named Vostra.