More and more PC users leave their computers on all the time, but after a few days of usage, the chance of a system crash increases dramatically. This phenomenon-known as "aging"-occurs from a steady accumulation of the small programming errors common in software. There's no cure for aging except to reboot the system, but now researchers at IBM, led by Tom Bradicich, have developed a software rejuvenation program that can predict when a computer is close to the edge and warn users it's time to reboot. The software is built into the latest version of IBM Director, the software that runs on IBM's low-end servers. Bradicich says the program could be modified for use in other Windows and Linux computers. -E. Brown