RE: Pc not booting; monitor in standby.

my brother installed directx9 off a dodgy copy of NeedForSpeed and after it reset to complete the install the computer has stopped booting. I have stripped the computer down to mainboard,vga,floppy,memory,cpu. All the fans turn, cdrom and hdd light up on power on but no beep from the motherboard at all and the monitor led remains in standby. The hdd stays lit for a good few seconds(when connected) but i'm sure windows aint loading
I have tested power supply with an atx tester, and cpu runs cool always, and have cleared cmos, no luck
I am suspecting my bios has been wiped, but i cant find a virus on the installation disk (only a file with an invalid start address) how do i diagnose bios failure. i cant even boot from floppy to try reflashing it.

Try pulling the VGA adapter and memory.

On most systems BIOS/POST would still be able to run and give you a memory error beep. (Assumes speaker hooked up.)

If no beep(s), then either system board (with BIOS) is bad or the processor is bad.

It is very unusual for the BIOS to be wiped, most likely a processor failure or a board failure.

If you just installed a software update and your computer went south, why would you not suspect the software? Try doing a registry restore. From the command prompt type Scanreg/restore and select a registry backup file that predates the problem.

You have the right idea to suspect the bios is not running. But the chances of it being the Bios chip itself is extremely slim. The motherboard and CPU have to also be working for the bios to run.