IBM ThinkPad X31 On its own, the ThinkPad X31 weighs 3.7 pounds, which is virtually identical to the weight of its closest competitors, the Dell Latitude D400 and the HP Compaq nc4000. Yet it's a little smaller than both of these rivals, measuring 10.8 by 8.8 by 1.4 inches. Speaking of typing, the ThinkPad keyboard is smart, as usual. Its 87 keys are logically arranged and have a nice feel, thanks to a 2.5mm keystroke. But because IBM crammed the slightly undersize keyboard (18.5mm key pitch) into the narrow notebook, things feel a bit cramped, and your hands tend to slide off the edges as you type. The pointing stick and the three cursor-control buttons work well--the scrolling feature is handy once you get the hang of it--but unlike the Dell and HP models, the ThinkPad X31 does not offer a touchpad. The 12.1-inch display has a maximum resolution of 1,024x768 pixels, typical for this class. The steel hinges and recessed bezel give the display a sturdy feel and add a little flair. The design also leaves room for a keyboard light--helpful when working in a dimly lit airplane cabin or hotel room. One of the first ultraportables to offer Intel Pentium M processors, the ThinkPad X31 remains the one to beat in terms of features. All models include either a 1.4GHz or a 1.6GHz Pentium M chip, 256MB or 512MB of system memory (expandable to 2GB), hard drives that range from 20GB to 60GB, and the ATI Radeon Mobility graphics chipset with 16MB of DDR memory. In addition to the usual VGA and parallel ports, the ThinkPad X31 has two USB 2.0 ports, a FireWire port, a single PC Card slot, and a CompactFlash slot that can handle Type II cards, such as the Microdrives now sold by Hitachi. The ThinkPad X31 has many little touches that improve usability, too, including a screen magnifier for zooming in on details, browser Forward and Back keys, the ThinkLight keyboard light, and the Access IBM button, which provides quick access to IBM's system help and bundled utilities that actually help you solve real-world problems and get the most out of the notebook.

The default OS is Windows XP Professional, but you can also choose XP Home, Windows 2000 Professional, Windows 98 Gold, Windows 98 Second Edition, or Windows NT 4.0 with Service Pack 6a. One reason for the ThinkPad X31's good performance was that the model we tested had an ATI Radeon Mobility graphics chipset with 16MB of its own memory. By comparison, both the Latitude D400 and the Compaq nc4000 use graphics chipsets that borrow system memory, which can be a drag on performance. The ThinkPad X31's scores varied slightly depending on whether we tested with the default battery or with both the standard battery and the optional extended-life battery, but either way the system was very fast. The ThinkPad X31 really shined in our battery tests. With its standard 10.8V, 4,400mAh battery, the ThinkPad X31 kept running for more than four and a half hours, easily outlasting both the Dell Latitude D400 (11.1V, 3,900mAh battery) and the HP Compaq nc4000 (10.8V, 3,600mAh battery). In fact, the ThinkPad X31's MobileMark 2002 battery score was a whopping 73 percent better than that of the Compaq nc4000.