It probably is a BIOS problem; but, there will be no BIOS update for antyhing that old.
Symantec used to have a software fix for this problem that ran in the DOS portion of Windows 9x (or 3.1) boot up. The best I remember, it was a free utility. I had it on hand for a long time; but, having not had a call about a Y2K problem in so long, I don't have any idea how long it might take me to find it (maybe even never).
Go to
www.google.com and do a search for
"Y2K Fix" -virus. You might get lucky; but, Y2K has been a non-issue for so long, I doubt it.