I'm having some issues with my self-built computer. I purchased the parts back in January and have had odd problems since. The specs are as follows:
 
Gigabyte GA-P35-DS4 Rev. 2.1 w/ F12 BIOS
Q6600 SLACR G0
Tuniq 120mm Tower
2x2gb G.Skill PC2-8000
eVGA 8800GTX
Antec TruePower Trio 650w
Audigy 4 Soundcard
Samsung SATA DVD+-RW Drive
Seagate 7200.10 320gb SATA
Western Digital 500gb SATA
Antec 900 Case
(Probably doesn't matter but:
Logitech G15
Razer Copperhead)
 
Now the problem I am having, is that the computer sometimes (more like 2/3 times) wont cold boot after being turned off overnite. I also usually have problems restarting the comp or resetting via the top switch. Now the computer is overclocked, I have tried various OC's ranging from 3ghz to 3.4, but have settled with 3.33 @ 371x9. Now I think the problem is with the board, because with that OC I can run Prime95 on all 4 cores for 9+ hours with no errors at all, and with temps never going about 58c on the hottest core. My ram is being run at a 2.5 multi with the comp at 5-5-5-15 as per manufacturer specs, and have found it stable at 4-4-4-12 when I am running the comp at 400x8 with the ram 1:1 with the FSB. I am currently running on Auto voltages in the BIOS to see if the voltage is an issue, but I don't think it is. My videocard is overclocked, but that doesn't seem to affect the problem. I have tried the F10, F11, and F12 BIOS's with and without Loadline calibration on and it doesn't seem to make a difference. I have also tried running the machine with the different levels of performance the BIOS has options for (Standard, Turbo, Extreme) and have made sure to disable the Auto-Load OC settings. What my computer will do is get right about to the point where it would detect the IDE drives (Sometimes it will detect them) and then shutdown, only to turn on about 5 seconds later with some of the OC options defaulted (i.e. if my multi was 8, it will default the FSB to its norm of 266, thus meaning my computer will boot up to the BIOS at 2.1ghz. Now the only thing that has seemed to cause/fix the problem, is when my WD MyBook 500gb Hard Drive isn't plugged in. I don't know if the times it's worked is because it wasn't hooked up, but before being able to boot up at any OC at all this morning, I had to disconnect it. Also, the computer will always run fine at the standard 2.4ghz (266x9) no matter what it seems like. But it's just annoying knowing that my computer will run stable OC'ed but only once it gets past the initial boot. Hopefully you guys can help me resolve this issue. Thanks!
 
EDIT: I just remembered, I don't know if it helps or not but when you OC on this motherboard, the board will shut off to apply the changes I would assume, then click right back on. Well I usually have issues with that, but then again it could be tied to the External HD and I have to turn the Powersupply's main switch off when the computer auto restarts, so that way when it goes to start up it will suck out the remaining power then turn off. Then I can turn on the comp and seems to take the OC. Not sure if I explained it well, but the process is pretty odd.