The Bios is the basic input and output system on a PC. It usually is stored on a read-only memory (Rom) chip and is the first code the computer looks for when it is booted.

One problem with the Bios is that Phoenix Technologies, a leading maker of the Bios software for PCs, changed its product only in 1995. Use of software from before that date to make Bios chips will produce a non-Y2K-compliant code.

This is what the Phoenix Web page has to say concerning the problem: 'Phoenix fixed this problem in February of 1995, but our customers [PC and motherboard manufacturers] may be using Bios source code purchased prior to February 1995. There is no Bios version number that guarantees your system will report the proper date in the year 2000.' What this means is that makers of Rom Bios chips who did not upgrade their software in 1995 continue to make chips that will not handle the year-2000 problem. It is also possible that older chips will be recycled and new machines could be sold with old Roms in them.