Video, motherboard, PSU problems... Experts needed
Here's the story. About a week ago, I got an ASUS 7800 GTX from Newegg. I installed in into my equally-new DFI LANPARTY SLI-DR board. For the first two days, it ran perfectly - top-notch in every single thing I threw at it. I was quite pleased.
Then, after 5 minutes of on-time on the third day, my computer spontaneously shut off. I fiddled a bit, perplexed; I ended up determining it was the power supply. My blue system fan LEDs would come on for a split second, then nothing. I rushed out to get a new power supply, thinking mine must not have been up to par.
Tragically (yet not unpredictably), that didn't solve much. Instead, for whatever reason, my new PSU (Antec 450W) would allow my computer lights to come on (and stay on), but my display was not working. I got distressed and tried two other monitors. No luck. At this point, my computer is on but not displaying video.
So I chocked it up to a semi-DOA card. But then I checked it out on another system - the card was fine. Here's where I started to overhaul it.
I replaced the RAM and tested the other sticks I had. They worked perfectly.
I replaced the motherboard with an ASUS KN8 ultra. No luck: PC fans and hard drive spinnage, but no video. Now I'm pissed.
I replaced the processor. AMD 3000+ Venice core (OC'd) to a 3500+ (no OC). Still nothing.
I tried different IDE cables and separate hard drives to no avail. Didn't think it'd work, anyway.
What on earth is going on here? I am utterly stumped.