My computer hasn't been working for a while now. It has the problem of when I press the power button, it will turn on for a split second, then turn back off. Sometimes it will stay on, but nothing will show on the monitor, and there's no beep from the computer sayin it's turning on (doesn't that beep usually sound? I think that's what i remember with my old desktop). The little screen with numbers on the Motherboard (I think it's the temp monitor?) read "FF."

I have yet to go buy a Power Supply tester, as I've heard the PSU might be the problem.

Here are my specs;
Motherboard: EVGA nForce 750i SLI Socket 775
Processor: Intel Core 2 Quad Q8200 2.33Ghz 4MB
OS: Windows 7 Home 64-bit
RAM: OCZ SLI 4096MB PC6400 DDR2 800MHz (2x2048)
HD: WD Caviar Green 1TB 32MB/SATA-3G
PSU: Apevia ATX - IB680W-GN (Iceberg) 680W
Video Card: EVGA GeForce GTX 260 Core 216 896MB