I recently changed Hard drives and Sound Cards and now my Computer turns on, but with no monitor. I can see the fan spinning, and hear the cd rom. I tried resetting the CMOS, Bios, checked the battery, Replaced the sound card with another.. I also tested the monitor and video card in another computer and everything is fine. the new hard drive is fine too. Any ideas? I can't even get to the BIOS to see it!

ASUS A7V8X-X Motherboard
512 DDR-RAM (verified it works!)
Standard Trident VGA Card (tried several)
No Sound Card at the moment
AMD Athlon 1.2 GHZ Processor
Power supply good, too.

if your PC has a reset button try pressing that during power up, sometimes the PC starts up so quick the cards dont get chance to see an older monitor or PCI graphics card

try replacing the ram if you can, so often the cause of grief