Computer will not even boot to bios

[Paradisetropica]

I have a computer that was built for me. It was running window 2000 and the power supply died.
I bought a new power supply and reloaded windows xp on it.
it was registered to another computer and i was just using it to test this one.
I did not register it. and all worked fine once i got all the bugs worked out.
I transfered the motherboard to another case and was going to reload windows 2000 and now it wont even boot to the bios. I removed everything and tried again and still nothing.
I was careul to not "shock it with static. It powers up the pcu fan spins and the floppy light stays on. it sounds like the Hd is spinning but the hd light doesnt come on on the front . Did I fry my mobo? what steps can i take to possibly fix this?

[Bro John (UK)]

Floppy or Hard Drives Cables may be plugged in the wrong way round, this sometimes causes a PC not to boot. Disconnect all drives, to test if motherboard is blown.

If mobo ok, then system will boot to bios.