A BIOS does not go wrong - it can't. So something else has changed. When the PC executes the BIOS code, one of the things that it does I look for BIOS 'signatures' in certain memory locations so that 'new' BIOS code can be added to support 'new' adapters. (For example that is how IBM added code for Hard Driver to the original IBM PC BIOS.)
So you need to remove any adapters that you can and then try booting the PC.
T
July 2010