The bug, which causes some subsystems to continue drawing power from batteries even after the device is switched off, apparently affects only handheld PCs manufactured by Casio. Casio markets the devices itself as Cassiopeia but also supplies the computer to Compaq, which markets the handhelds under its own brand name, the Compaq "PC companion."
"The service pack we worked on with Casio and Compaq makes sure all the subsystems get shut off," said Jim Floyd, product manager for Microsoft's Windows CE operating system. "It's more almost an insurance that the problem won't happen."
The problem apparently corrects itself when the device is switched on again, but if a user turns off the handheld device and doesn't pick it up for several days or weeks, the defect could sap all the battery power. When that happens, all data in the device would be lost because it does not have a hard drive. Instead, information is stored in RAM, which cannot hold data after the device has been switched off.
Casio apparently alerted Microsoft to the problem, which Compaq said none of its customers had reported.
"It's not something that the average user is going to see on a regular basis," said Annie Bacon, director of marketing for Compaq's handheld products. "We believe it's going to happen maybe once a year."
Nonetheless, Compaq is trying to reach people who bought one of the four models in its PC companion family so it can recommend the fix.
Bacon declined to say how many Compaq customers were affected by the problem. A spokesperson for Casio was unavailable for comment.
Compaq's handhelds are designed to be used with a PC, Bacon added, so most users will synchronize data between their PC companion and their desktop unit regularly, minimizing the impact of lost data.