That is changing. A new miniature-chip technology from Texas Instruments (TXN) called pico is making digital projectors truly portable, instead of merely luggable. For the past couple of weeks, I’ve been using two of the first pico-based projectors on the market, Dell’s M109S and Optoma’s Pico PK-101.

The products are designed for different customers with different needs. Dell (DELL) positions the 13-ounce M109S as a notebook companion, best suited for work presentations. The four-ounce Optoma projector is designed more as an iPod or digital-camera accessory for watching movies and slide shows on the go.

The Dell M109S

Their portability requires compromises, most obviously in brightness and image resolution. The Dell and Optoma projectors, respectively, support 11 and 50 lumens — a standard measure of projector brightness. That’s far dimmer than top-notch projectors that offer several thousand lumens. So neither product excels in well-lighted rooms, where overhead and ambient lighting overpower their images. You can compensate somewhat for this weakness by placing the devices closer to the surfaces onto which they’re projecting — for example, a wall. But the darker the room you use, the better.

At about the size of a candy bar, the $399 Optoma device is the smaller of the two projectors and the one with the most intriguing possibilities for expanding the tiny screen sizes of mobile devices like the iPod.

It’s powered by a rechargeable battery that Optoma says lasts for an hour on full brightness or two hours on a power-saving setting (the projector comes with two batteries). The projector has a tiny speaker, but people who want decent sound will need to use headphones or external speakers.

In theory, the Optoma device is small enough to bring along on a camping trip to show a film on the side of a tent, or to a restaurant, where you could inflict a vacation slide show on dinner mates by projecting onto a napkin or tablecloth.

I tested it on a recent airplane flight by projecting an episode of “Mad Men” from an iPod touch onto the back of the seat in front of me. The seat was a dark blue with embossing on it, so it didn’t work very well. It’s best to project onto an unmarked, light-colored surface. The quality of the image was better when I lay in bed one night, projecting a video onto a white ceiling.

Even under the most favorable circumstances, however, I found the images from the Optoma projector very dark, muddling the outlines of characters and action on screen. Although Optoma says you can get up to a 60-inch image from the projector, 45 inches was about as big as I could make the image before it got too fuzzy.

Optoma says the projector will ship with an iPod-compatible connector cable when it goes on sale in the U.S. on Dec. 15, though the unit I tested didn’t come with one. I connected the device to my iPod touch using a $50 cable from Apple (AAPL).

Compared with the Optoma device, the $449 Dell M109S is a behemoth, yet it’s still only about the size of a short stack of drink coasters. Most projectors weigh at least a few pounds, if not more, which is big enough to make them a hassle to carry around. I barely noticed the Dell projector inside my laptop bag.

Unlike the Optoma projector, the Dell M109S has to be plugged into an electrical outlet to work. It comes with an unsightly set of connectors for plugging the projector into a video source, such as the VGA port found on most laptops and a composite video plug that is standard on DVD players. I was, however, able to plug my iPod touch into the Dell projector using the $50 Apple cable.

And unlike the Optoma, the Dell doesn’t have speakers. To get sound for a movie, you’ll need headphones or speakers, like those on a laptop.

Despite its extra bulk, the Dell M109S literally outshines the Optoma projector. It produces a bright image that I found very watchable, even if it wasn’t high-definition. I projected the movie “James and the Giant Peach” onto an interior wall of my house, creating an image that was about 7 feet, measured diagonally.

The Dell M109S includes a capability called keystone correction, a standard feature in most projectors that adjusts a projected image to give it the proper dimensions, rather than the trapezoidal shape that results when a projector is angled upward. The Optoma projector doesn’t have this feature. To get a normal rectangular movie image, I had to hold the projector level, toward the projection surface.

For business travelers who do presentations or for people who want to create a theater-like experience in a hotel room, vacation house or against a sheet in the backyard, the Dell projector would be a good fit. For now, the Optoma projector is a good idea that needs refinement.

• Email Nick.Wingfield@wsj.com. Walt Mossberg is on vacation.

About 18 months ago, the giant PC maker brought out an unusual desktop computer called the TouchSmart, a bulky model meant for kitchen counters. It was intended as a walk-up home kiosk, with large icons you could activate by merely touching them to check the weather or to consult your calendar.

This TouchSmart was praised for its originality, but it wasn’t as practical as promised, and wasn’t a big hit. Still, H-P is persevering with the concept. It has refined the hardware and the touch-controlled software, and has come up with a new line set to go on sale by mid-July.

This new TouchSmart, which comes in two models priced at $1,299 and $1,499, is a relatively slim, one-piece desktop with a large 22-inch screen. It resembles the Apple iMac or the Dell XPS One and, like the latter, runs Microsoft’s Windows Vista. It has a wireless keyboard and mouse, and can be used as a normal Vista computer.

But, like the first TouchSmart, this new model comes with H-P’s touch-controlled user interface and special programs designed to be manipulated with your fingers. For this model, H-P is de-emphasizing the idea that the machine is meant for the kitchen, but it is forging ahead strongly with the notion that touch control is the wave of the future.

After testing the new TouchSmart PC for a few days, my verdict is mixed. The TouchSmart software is indeed improved. It’s attractive, more versatile and more practical — and fun to use. The hardware is handsome and well-equipped. And H-P deserves credit for continuing to build software expertise in a world where makers of computers and cellphones must become as expert at software as they are at hardware. But the latest effort has some problems.

The TouchSmart interface is inviting. There’s a top row with huge icons, called tiles, displaying your favorite programs, and a bottom row of smaller tiles for other programs. You can scroll each row with a finger and decide which programs go in which row. You can even include in either row not only TouchSmart programs, but the regular Windows programs or Web sites that you like. When you tap on a tile that isn’t for a special TouchSmart program, the computer pops you into the regular Windows interface. To return to the TouchSmart interface, you just tap a home button below the screen.

Hewlett-Packard’s TouchSmart

The TouchSmart software includes a calendar, a weather widget, a clock, music and video players, a program for composing short notes, and even a basic Web browser. All worked OK in my tests, but they’re simple and limited.

The computer itself is fairly powerful. Both models have dual-core processors, large hard disks, and a whopping 4 gigabytes of memory. And both run the special 64-bit version of Vista, which allows more memory usage and can be much faster than regular Vista, but only if you buy special 64-bit software programs. This machine is loaded with every conceivable port and connector, mostly hidden from view, and the high-end model even has a TV tuner.

But this is still a Vista computer, with all of the disadvantages that entails, especially a sluggish start-up and an annoying barrage of pop-up warnings. And the new TouchSmart is preloaded with craplets, those irritating trial programs and come-ons that you didn’t order.

There’s a built-in Webcam that works in low light, but it’s almost impossible to tilt the computer forward to get the best shot. Plus, the TouchSmart software interface is very basic and is ragged around the edges. It isn’t a multitouch interface — like the ones on the Apple iPhone and in the next version of Windows, code-named Windows 7, that recognize a variety of gestures and perform different tasks when multiple fingers are used rather than just one. For example, you can’t rotate a photo on the TouchSmart by grabbing it with your fingers, or move back and forth through Web pages by swiping the browser with your fingers.

The TouchSmart software is just a thin shell plopped on top of Vista, and it crashed on me four times during the course of a few days of testing. Also, the limitations of the TouchSmart applications can be frustrating. The photo application wouldn’t let me create albums. The music application didn’t display artist names for some of my MP3 files, and the calendar application can’t display an onscreen reminder of an event if you’re working in the main Vista interface.

If you’re intrigued by the idea of a quick and simple interface on a handsome one-piece Vista machine, the TouchSmart might make sense. But it doesn’t deliver on the full promise of touch computing.

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

As always, this is a general guide aimed at mainstream, nontechnical consumers who dwell on common tasks such as email, instant messaging and surfing the Web; managing and lightly editing photos, videos and music; and using basic office applications. It is not intended for heavy gamers, video producers or corporate buyers.

There’s a vast variety of laptop models, but this guide is meant to cover the most common types of laptops, those with screens from about 12 inches to 17 inches, and weights ranging from around 2.5 pounds to 7 pounds.

For this column, I’m not including the category of tiny machines now called netbooks, with screens under 10 inches. I am also ignoring the huge, heavy laptops with screens larger than 17 inches that are primarily aimed at gamers.

Even the remaining mainstream machines range wildly in price, from bargain-basement models at $350 to high-end ones that can top $3,000. In my experience, the top brands for technology and reliability are Apple and Lenovo’s ThinkPad line, but various models from Sony, Hewlett-Packard, Toshiba and Dell are also worth investigating.

So, here is a quick guide to the key factors you should consider when buying a laptop.

Size: If you are a constant traveler, think about the subnotebook models, which generally weigh 3 pounds or less. There are two types of these. The classic subnotebook has a small screen, 12 inches or less, and a cramped keyboard. This year, a new type emerged, with a full keyboard and a normal 13.3-inch screen packed into a thin, light body. There are two of these: the MacBook Air from Apple and the Lenovo ThinkPad X300. All subnotebooks are relatively costly, typically ranging from $1,500 to over $3,000.

If your laptop will mostly stay at home, the office, or in class, a 5-7 pound machine with a screen of either 13.3 inches or 15.4 inches is the best bet. A well-equipped model in this class is likely to run you between $800 and $1,200. Typical models in this class are the Dell Inspiron 1525, the HP dv6700 and the Apple MacBook.

Windows vs. Mac: This is the eternal question. In my view, Apple’s Leopard operating system is faster, better and far less prone to malicious software than Microsoft’s Vista operating system. And the Mac laptops also come with better built-in software. The $1,099 MacBook is a solid, fairly priced machine, and the $1,999 MacBook Pro is even better. Both also can run Windows.

But Windows laptops are often less expensive, tend to have a greater variety of ports and slots, and come in more styles and sizes.

Apple’s MacBook

Operating system: If you are buying a Windows laptop, be aware that Vista is slower than Windows XP, in my experience, and still has compatibility issues with add-on hardware and software. If you’d prefer to stick with XP, you will find that many fewer models are available with it. And Microsoft has decreed that after June 30, mainstream, name-brand laptops will no longer come pre-equipped with XP.

Video: I recommend getting an LED-powered screen, which is brighter and saves power. Also, if you are choosing Vista, or if you do a lot of converting video for use on portable devices, consider getting a laptop with a separate video card inside that has its own memory.

Memory: If you’re buying an Apple laptop, two gigabytes of memory is plenty. If you’re using Vista Home Premium, I’d consider three gigabytes for best performance.

Processor: Any dual-core processor will be fine. Don’t pay a penny extra for faster processor speed.

Storage: In a mainstream laptop that will be your main computer, look for a 160-gigabyte hard disk or larger. A new kind of storage, called SSD, or solid state disk, is now available. But it is still way too costly for most users, and at the moment is available only in smaller capacities.

Battery life: Many laptops today rarely spend time away from an electrical outlet. But if yours will, look for a battery life of at least three hours between charges.

Wireless: Make sure your new laptop has the new, faster “N” version of Wi-Fi built in. Many cheaper laptops don’t. You can also get a cellphone modem built in, but they are costly and carry a monthly fee. You can always add an external cellphone modem later.

Other features: A built-in camera and microphone can be quite useful, and so can a feature on some Windows machines that allows you to play music and videos without fully booting up the computer.

Don’t let yourself be swayed by sales pitches, or by fanaticism for or against Windows or the Mac. Think hard about how you use your computer and what your budget will allow, and stick to those priorities.

• 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.

But this isn’t the much-touted Apple MacBook Air, introduced last month with all those qualities. Instead, it’s a new ThinkPad from Lenovo, the X300. While the two machines are both impressive products, they are different in key respects.

I’ve been testing the ThinkPad X300 and I have found it to be a solid, innovative laptop that will be perfect for many mobile PC users. It isn’t as sexy or inexpensive as the MacBook Air, but it has numerous features the Apple lacks, especially a wide array of ports and connectivity options, a built-in DVD drive and a removable battery.

I can recommend the X300 for road warriors without hesitation, provided they can live with its two biggest downsides: a relatively paltry file-storage capacity and a hefty price tag. This ThinkPad starts at $2,476 for a stripped-down model and at $2,799 for a preconfigured retail version with a half-size battery. The configuration I expect to be the most popular, with a full-size battery and DVD drive, is about $3,000.

The key factor in both of these downsides is the solid-state drive, or SSD, which replaces the hard disk. The SSD is fast and rugged, but today it can hold only a cramped 64 gigabytes of files and is very costly. Apple offers a MacBook Air version with the same solid-state drive for a similar high price. But Apple also has a much more affordable $1,799 model with an 80-gigabyte standard hard disk. Lenovo doesn’t.

Lenovo’s ThinkPad X300

The X300, due to go on sale next week at lenovo.com and at a few retailers, isn’t as thin as the MacBook Air. In fact, at its thinnest point it is almost as thick as the Apple is at its thickest point. And when the new ThinkPad is ordered in what are likely to be its most common configurations, it is heavier than the three-pound Apple and, in fact, fails to make the three-pound cutoff that typically denotes a “subnotebook.” Only one configuration breaks that barrier, at 2.93 pounds, and it is the stripped-down model with just a half-size battery and no DVD drive.

But the X300, which will come with either Windows Vista or Windows XP, is still very thin and light. It’s under an inch thick and even at its heaviest is only 3.5 pounds. Yet, like the Apple, it packs in a widescreen 13.3-inch display and a full-width keyboard.

Plus, Lenovo has used that extra thickness to good advantage. While the MacBook Air’s extreme thinness makes it gorgeous, it left no room for an Ethernet jack, a removable battery, a built-in DVD drive or a cellphone modem. The X300 has all these things, either standard or as options, plus three USB ports, compared with just one for the Apple. The Lenovo even offers GPS location-finding, the ability to connect to new wireless USB devices and future support for a forthcoming wireless network standard called WiMax.

The ThinkPad has another advantage: Even though its screen is the same size as the Apple’s, it is higher resolution, so more material can be seen without scrolling. Some people find that higher-resolution screens make text too small to read easily, but I didn’t experience any such problem on the X300.

In my tests, the X300 performed very well, even though it has a relatively slow processor, slower than the MacBook’s.

But the ThinkPad’s battery life was only fair, and was inferior to the Apple’s. In my tough test, where I turn off all power-saving features, set the screen to maximum brightness, turn on Wi-Fi and run a repeating play list of music, the X300 lasted three hours and five minutes. That was 24 minutes less than the comparable MacBook Air. And this was on the $3,000 configuration with a full-size battery and a DVD drive. The more basic models, with a half-size battery, would last only half as long, according to Lenovo.

MacBook Air

In more normal use, the model I tested would likely last under four hours on a charge, and the base models maybe two, compared with about 4.5 hours for the Mac.

I also tested another version of the ThinkPad, which substitutes a second, half-size battery for the DVD drive. It got five hours and 15 minutes, which means you could likely get 6.5 to seven hours in normal usage. That model costs around $2,850.

There are two more factors worth mentioning. I believe that both the Mac operating system and the software that comes with it are superior to the Windows operating system and built-in software offered on the ThinkPad. And the Mac isn’t susceptible to the vast majority of viruses and spyware, and doesn’t require third-party security software.

Also, the ThinkPad’s screen, when opened, stands significantly higher than the Mac’s, so it is less usable in a coach seat on an airplane when the person in front of you reclines.

If you’re happy with Windows, can afford the price tag, and value the many ports and connectivity options Lenovo has packed in, the thin and rugged X300 is a great choice. It’s a notable engineering accomplishment.

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.