Have a look here pick your mobo or bios and see if the code is listed-:
'Bios Central' (
http://www.bioscentral.com/)
Pretty sure error 25 on a Abit is related to the Graphic card, could be
wrong mind.
You'll get bios boot and be able to access the bios with just the CPU,
RAM and Graphic card, all the rest can be disconnected and ignored,
including the hard drive.
Best plan is 'BTB' Back to Basic's, aim at getting the bios to boot
otherwise nothing else will happen, check all the links and clocking
speed settings or restore it to as it was when it was working.
Maybe there is a reason that you wanted to swap the Graphic card, would
there be any clues here and was the machine working perfectly prior to
changing the card?
Davy