Hey guys ... posting here after replacing intel e6600 cpu and P5N32-E SLI motherboard in attempt to get this homebuilt rig to light up the monitor, keyboard and mouse. Was getting a message in BIOS "cpu has changed" ... this problem (the harddrive seems to fire up but now the monitor and peripherals do not start up anymore) has been progressive .. meaning for a while I could simple re-start and the computer would eventually start. Occasionally booting from the windows install disk would apparently do the trick. Now Nothing seems to do the trick. I have attempted to link a borrowed IDE drive into the chain as way to see if the WD Raptor Hard Drive is at fault, but no luck there either. Any thoughts on what to try next?

Sounds like a hardware conflict. Strip it down to just the Power supply, motherboard, minimum RAM, keyboard, mouse and monitor. If you have onboard video, use that and remove your video card. Get into the BIOS and set it to DEFAULT settings. Then, add one component at a time and see what gives problems.