Is this the same M507 motherboard from your other post?
I've read the contents of the BIOS chip from my M507 board in a programmer quite recently, though I haven't been able to determine exactly what type of chip it is as a Google search of the writing on the chip brings up nothing. As such I haven't been able to erase or write anything to it.
It's certainly not a UV eraseable EPROM as suggested above, but it could very well be a one-time programmable ROM chip and as such you'd need to order a replacement programmable DIP32 1M chip & an external programmer to upgrade the BIOS. I myself am currently waiting on an Atmel 29C010 that I've ordered from China, as that particular chip is referenced as compatible here: http://th2chips.freeservers.com/m507/bios/index.html
I did try a UV eraseable EPROM chip as a potential replacement - an ST Microelectronics M27C2001. But the board wouldn't POST at all with that chip, hence why I ordered the Atmel instead.