I felt it would best be put here because it is a custom pc. I noticed the fan was a little louder so I opened the case to clean out some dust. I blew off the processor and fans and reinserted. I did forget to turn off the power supply when I did this. I also unplugged a cable that plugs into my motherboard from my power supply because it was in the way of my processor. I tried once to start it up and no image came onto the monitor as if it weren't plugged in. I forgot to plug back in the cable to the motherboard. When I pluggedit back in my computer wouldn't start up. At this point I turned the power supply off for a few moments, then back on. The computer fired up its normal bios and made it to the desktop. While I was closing the side my comp shut down suddenly. When I rebooted it said it overheated. Which it was only no more then a minute. The overheat message was pre-bios and the bios ran fine afterward but it still shuts down and claims it overheated after about 1 minute of running. Just some direction as to how to approach this problem would be greatly appreciated. Please tell me if what I'm saying is clear enough.

Asus pgx580 motherboard
corsair tx 750 watt
I7 processor
Geforce GTS 250
Windows 7 Premium 64-bit

EDIT- I also do not overclock or do any modding, and I feel I kind of rambled above O.o

Did you remove the heatsink fan (HSF) assembly? If so, did you apply a fresh new layer of TIM and did you ensure the HSF is properly seated and secured?

I went to apply more TIM and had to be conservative. Only a few drops left off to the Electronics store. But I think that is most likely the answer. I'll update in an hour or so.

Only a few drops left

That may be enough. Remember, too much is in the way.

SOLVED
All apoligies for not getting back. I had to goto work and forgot to post later. Anyway, it was the issue. Thanks a million.

Glad you got it sorted out. Thanks for the update.