Hardware problem: Dead desktop

[Mark M Lambert]

Hello all, I know this is not a Ubuntu problem but I don't know who else
to ask. My desktop PC has died, or appears to be brain dead. When I
power up the power supply appears to work - all the fans come on, I can
open and close DVD drawer, and the power LED illuminates, but then the
PC just sits there. Screen remains black, no hard disk activity. 
I think the CPU is cooked, but no idea how to test this or isolate the
problem component. Can anyone give me ideas, or does anyone know someone
in Sydney I can take it to that won't rip me off.

Thanks heaps
Mark