Alright, have I got a story to tell! (I apologize beforehand for the lengthy post, but I want to be as thorough as possible)
I built my pc from the ground up, and everything seemed to be working fine at first. It uses two g-force 7900's, a duo pentium processor, a AMD socket AM2 processor motherboard, and 2 gigs of ram, and (at the time I built it) a 550 watt power supply. After about two weeks or so, my pc began to act strange; when I turned off my computer, it would turn itself back on after about 15 or 20 seconds, as though I had hit the power button myself. Then, about 5 days later, my power supply burnt out. I bought a larger 700 watt power supply shortly after that, but my computer continued to turn back on after I shut it down. I figured I'd just make sure to shut off my power strip after I shut down my computer and ignore that annoyance, and for about 2 months or so that seemed to work fine. Then, two days ago after I woke up, I turned on my pc, and did about 10 or 12 minutes worth of work when the monitor simply shut down. My computer's lights were still on and it was still working (as far as I could tell) , yet the monitor was simply off. I figured the monitor was at fault, so I tried a different monitor, and the same thing happened! I tried re-seating my two graphics cards, then a different thing happened; instead of the monitor shutting down, my pc would simply lock up after a few minutes. Then the blank screen happened another couple of times. Now I hear a wierd soft "ticking" sound sometimes when it boots up, and get a windows error message (you know, when it asks if you want to start up windows normally, or from last good configuration) but my keyboard wont work to select any option at that point, until the timer runs out and it selects "start windows normally" and goes to the desktop. I figure the ticking sound is from my hard drive, since it usually coincides with that error message. I am quite simply flabbergasted. This pc is only a couple of months old, all the parts were bought new at newegg.com, and its plagued with problems. I figure the gfx cards, ram, and processor are fine. So that leaves either the hard drive, motherboard, or new power supply may be to blame. The ticking sound points to the hard rive, but could the hard drive be responsible for the monitor shutting down? I would greatly appreciate any and all help!

How did the power supply burn out? Details please.

Are you running these cards as SLi bridged?

Are the cards individually powered via dedicated lines from the PSU?

Clicking is usually a hard drive yes.

Can you enter the BIOS Setup?

Thanks so much for the speedy reply, I really appreciate it

Hmm, well the original power supply worked fine for the first two weeks, but one day my computer simply refused to turn on. I tried another outlet and tried the power button again but nothing still happened. Me and my friend opened up my comp and noticed a faint smell coming from the power supply. We broke the warranty seal and opened the power supply itself, and sure enough there were several burnt wires awaiting us inside. I did some checking on that particular brand and found several complaints of instability and burn-outs so I bought a new higher-power supply from a different brand. As for my gfx cards, I do sli them together, and they are indeed both powered from individual lines from the psu. And I can enter the BIOS setup (when my pc lets me, sometimes I think its being a jerk on purpose ) Dang I guess I better back up my stuff on dvd's ASAP if my hard drive is making noises like that at the very least

Who is the manufacturer of the hard drive? Most have diagnostic tools downloadable from their web site.

Just as a test I would remove the SLi bridge and try using the upper card for your monitor connection. Just to see if it makes any difference.

There are a lot of little details in troubleshooting and trial and error approaches. I, myself, am about to crash but will be back tomorrow.

Thank you so much for that advice about the gfx card! I did what you suggested and fiddled with both of em; I took out the bottom card and ran my pc with the top one I've been using since the beginning, and the problems started right away. I then noticed the ill-fated ticking sound coming from inside the case, and upon closer inspection, noticed it was coming from inside the graphics card itself (wish I had noticed that sooner...). I took that card out and used the bottom one instead, and sure enough my comp started up like normal! So I guess one of my graphics cards is faulty, but hey, one working card is better than none, am I right? I'm hoping that that gfx card is the reason for the random restart deal (maybe the retarded card would have trouble shutting down properly when I hit shut down and that would somehow trigger the reboot maybe?). Anyway I'm gonna keep an eye on it for a while and see what happens, but in any case thanks a butt-load dude! Maybe the curse has been lifted off of my poor computer at last

Thanks for the update and the thanks!

Was it the fan that was clicking?

If so you can open the card case and try to fix it. Or if still under warranty return/replace it.

Hmm I'm not sure, but i'll check it out and see, I kind of grew attached to the little guy; it'd be a shame if I had to scrap it! If all else fails I probably will try and get a replacement from newegg if the warranty isn't already up, but I think in a perfect world I might end up selling off my last working 7900 and upgrade to something with a little more firepower...say a 8800 (if I ever get the xtra dough that is lol). Thanks again mate!