IBM has added its first integrated fingerprint reader to select models of its flagship thin-and-light laptop, the ThinkPad T42. The sensor, embedded in the lower-right palm rest, requires that you slide a finger three times across its small window to register it. The included fingerprint software then merges the swipes into one image ID. The system protects the laptop and replaces cumbersome passwords.

Like the sensor found on the Fujitsu LifeBook P7010D we tried previously, we found IBM's slide sensor a bit more time-consuming to use than the older contact sensor windows that most fingerprint-reader-equipped laptops use. It's harder to slide a finger across a tiny sensor three times in exactly the same way than it is to merely press a finger in the comparatively large postage-stamp-size window used by contact sensors. It took us five tries--15 swipes altogether--to register our finger on the T42, and later, several tries to get the laptop to recognize our registered finger. By comparison, it usually takes only a couple of tries to register a finger in a contact sensor window. On the bright side, slide sensors can make a larger image of the finger being read, which gives the match software more data to analyze and theoretically results in tighter security.

The lightweight (5.4-pound) T42 is incredibly thin--just 1.1 inches tall with the 14.1-inch screen closed--and offers IBM's great keyboard with both eraserhead and touchpad pointing devices, each with their own smoothly working mouse buttons. The ThinkLight, an LED in the lid that a keystroke combination activates to shine a light on the keyboard, is a useful feature that helps when working in dim light.

A slim combination DVD-ROM/CD-RW optical drive came with our test model, but you can opt for a DVD burner ($349 extra) instead or buy a second hard drive to swap into the Ultrabay Slim modular bay. The modular bay also takes a secondary battery, but with the high-capacity, 9-cell battery that comes standard with the configuration we looked at, you won't need it. This super-duper battery, which extends the footprint by about an inch in the back, gave us a little over 5.5 hours of valuable working time in our tests. On the performance side, the T42 was a little less impressive but still within reasonable boundaries for its processor. Our 1.8-GHz Pentium M 745-equipped unit earned a WorldBench 5 score of 77, compared with a score of 80 earned by a Dell Inspiron 700m with the same processor.

The T series continues to suffer from a few relatively minor limitations. The connections are fairly modest--the T42 we reviewed lacked a FireWire port or any type of memory card reader beyond PC Card slots, and has just two USB 2.0 ports. However, IBM offers docking options galore, ranging from a simple port replicator to a full-fledged docking station. The T42 stays true to IBM form with forgettable stereo sound.

The T42 should be relatively easy to upgrade. Only one memory slot is user accessible, in a bottom compartment, but you can pull the slim hard drive out of the right side of the case with your fingers. Just open the laptop's screen and remove one security screw on the bottom of the case. The ThinkPad's animated user manual is unsurpassed, with loads of helpful information and a troubleshooting guide.

Upshot: The T42's integrated fingerprint reader takes some patience to use but should reward with increased security. This notebook remains a top pick for business travelers.