I have an 8 year old computer (Pentium 4 1.6 GHz, 256 MB DDR RAM) which is not turning on (it beeps for 10 seconds and then goes off). Nothing appears on the screen, so I can't get into the BIOS.

A computer repair person listened to the beeping pattern and told me that its because of the integrated graphics on the motherboard is defective. It's an ASUS P4S333-VM motherboard and the graphics solution is SiS 650. He tried putting in a PCI graphics card expecting that the computer will use that instead and ignore the integrated graphics, but apparently older computers don't switch automatically to the dedicated graphics card; it needs to be changed from the BIOS. But, I can't get inside the BIOS settings as I already said. I am told that the only option now is to replace the motherboard (which is not feasible since it's very old now).

So, is there any way to make the computer use the PCI graphics card? IIRC, the motherboard also has an AGP port, but I think that it will also need to be selected from the BIOS?