Ill include a long detailed version of the problem as well as a brief overview.
I would like to start by saying this is around my 9th or 10th computer I've built in the past 6 years. All parts are compatible and there is more then adequate power supplying the computer.
The problem started when I first turned it on. I was able to get windows 7 installed, then when it first booted up it would stay on and it seemed like it would randomly restart every few minutes. after a bit of troubleshooting I felt it was a graphics card because I noticed it would restart whenever I used a program that used high graphics, so I swapped out the card with a known good one, same problem. then I swapped out the processor with a known good one and same problem, then I removed all my ram and tried them all one by one in different spots, same problem, then I swapped out the mother board, same problem. which left only the power supply. upon examination of the power supply I realized it was not the one I had ordered, and it wasn't of sufficient power to run my computer. So I got the correct power supply.
for the first day it seemed to be running spectacular, but the next morning when I went to turn it on it would not boot, all lights and fans came on, and the load light stayed on non stop, but the keyboard never lit up. I took the computer apart checked everything again and I could find nothing wrong so I gave up for the day, next morning It booted up just fine. and ran perfect all day. it continued to run fine for about a week, then I go to turn it on and it powers up load light comes on and nothing happens.
after this happened a few times I noticed that If I killed power to the computer for about 4 hours after this would happen then turn it on, it would work just fine. Now the other day I left to buy a pack of smokes, when I came home the screen was black and the computer was on, but nothing displayed. So I unplugged it and waited. nothing happened, I completely took it apart checked everything, and found nothing. and now it is working fine.
in short my computer will run for a few days or weeks then it will just stop working, turning it on lights it up and runs the fans but it never gets to bios. when power is removed from the computer for a period of time it comes back on.
I'm out of ideas on whats wrong. and suggestions would be much appreciated. below is my system specs.
I have monitored the heat for some time, and it has never been a problem. as for the heat sink its a Thermaltake Spin Q CPU Cooler . I know the power supply is big, but in time it will be put to use on a project im working on, for now im just focusing on getting the computer running properly. as for the PSU, I have tried my friends and nothing changed.
its not always 4 hrs until it works again, this last time it messed up took 2 days before it would come back on.
Your best bet might be to replace each component 1 by 1 with known working components (Again, with the new PSU). It might take a long time to eliminate each culprit but chances are one of your components is damaged.
My only other suggestion would be to check your mobo standoffs and all your cables to make sure something isn't shorting somewhere. Make sure all the connections are secure. Internally one of the cables could be bridging two lines (low impedence between them) which would cause things to malfunction.
Granted all of these things are mostly guesses. These kinds of problems are not fun to work on and I wish you luck.