This is particularly true of Windows laptops. If you're considering a Macintosh laptop, the process is fairly straightforward. There are only two models, the $1,599 iBook, available in only one configuration but two colors; and the costlier PowerBook G3, available only in black and starting at $2,499.

Windows laptops, however, come in a bewildering variety of sizes and brands, with all sorts of configurations. So here's a general guide to buying a Windows laptop.

Size and Weight: The first thing you need to decide is the general size and weight of the laptop you need. At the light end is a group of machines weighing just three or four pounds. These models, which include the Sony Vaio 505 series, the IBM ThinkPad 240, the Toshiba Portege 3025 and the Compaq Presario 305, are designed for sheer mobility. They lack internal disk drives and in some cases lack all of the standard ports, which reside on an external module. In this group, I prefer the ThinkPad 240, because in my view it has the best keyboard and pointing device, and it has built-in ports.

At the other end are machines weighing twice as much -- seven pounds or more. They tend to include every bell and whistle, such as huge screens and DVD drives. Such machines are essentially desktop replacements, meant mainly to stay in one place and to be moved only rarely.

These polar-opposite machines are the costliest. The lightweights run around $2,000, and the behemoths can easily top $3,000. But there's a group of laptops in the middle, in most cases weighing around six or seven pounds and selling for between $1,200 and $2,000. These machines are pretty well equipped, but they have somewhat less oomph than the heavyweights. They include the Toshiba Satellite series, the IBM ThinkPad "i" series, the Compaq Presarios and Hewlett-Packard's new Pavilion laptops.

Like the high-end boxes, they are mainly desktop-replacement machines, though they can also be carried by people who travel and need the built-in CD-ROMs and other bells and whistles missing from the real lightweights.

Screen: The best screens are made with a technology called TFT, and most laptops today have them. The low-priced models, like Toshiba's $1,199 Satellite 1555 and Compaq's $1,199 Presario 1245, have a cheaper, less vivid screen technology called dual-scan, or HPA. But check these out. You may find you can live with them. Size does matter in screens, and on high-end, high-priced laptops, you can get up to a 15-inch screen, comparable to a desktop monitor. But in most cases, I think 12-inch screens are fine, and much cheaper. If extreme mobility and light weight are important, you can do quite well with a 10.4-inch or 11-inch screen.

Whatever the size, make sure the screen is capable of a resolution of at least 800 by 600, also called SVGA in technobabble. This is a figure that governs how much material can fit on the screen.

Power users will prefer a resolution of 1024 by 768, also called XGA. High resolution can often compensate for a smaller screen. For instance, IBM's hefty ThinkPad i 1420 has a 13-inch screen, but it uses the weaker HPA technology and gets 800 by 600 resolution. Sony's Vaio 505VX weighs just three pounds and has a much smaller, 10.4-inch screen. But it's a sharp TFT model that gets a higher 1024 by 768 resolution.

Keyboard: This is a subjective thing, but in general I prefer IBM's laptop keyboard to everybody else's, even on very small models. I also prefer the pointing stick, used by IBM and Toshiba to emulate a mouse, to the touch pad used by many others. Dell's Inspiron 3500 offers both types of pointing devices. Battery Life: On a heavy desktop-replacement machine, which will spend most of its life plugged in, this isn't a key factor. But travelers will want the battery to last at least three hours and possibly more.

The new Apple iBook is a champ, at 4.5 to six hours. Alas, the very lightest three-pound machines, except for the Toshiba Portege, tend to get less than two hours, requiring you to tote extra batteries that offset the weight savings. The Toshiba gets about three hours.

Speed and Capacity: If you're using a laptop heavily, especially as a desktop replacement, then I suggest you get the same basic specs as on a desktop: at least 64 megabytes of memory, a six-gigabyte hard disk, a CD-ROM and floppy drive, and a processor running at 350 MHz or higher. A laptop like this will cost around $2,000 and up. If you're using a light laptop as an adjunct to your desktop, you may be able to settle for a slower processor, no CD-ROM and a smaller hard disk.

However, I don't recommend using less than 64 megabytes of memory. Add memory if necessary.

Remember, with laptops, a lot of the buying process is subjective. The look and feel of the machine, the touch of the keyboard, the look of the screen, even the size of the electrical adapter are pretty personal issues. But these basic guidelines should help.

(www.ptech.wsj.com)