I tried a BIOS upgrade to an ASUS A7V motherboard which failed and I was left with a dead machine. I managed to get the BIOS chip reprogrammed with original version, still machine dead. No bleeps, monitor does not come out of standby, drives would whirr for a few seconds and CPU fan works.
Decided motherboard must be damaged and replaced board with a Asus A7N8X. Machine still dead with new motherboard, videocard & monitor work fine with another computer.