Problem with reboots. Maybe RAM?

[Jayfaas]

My specs are as follows.

PC Power and Cooling 750W silencer PSU
74GB WD Raptor HDD on SATA
DFI LanParty P35-T2R motherboard
4GB G.skill RAM (http://www.newegg.com/Product/Produc...82E16820231145)
DVD Burner drive(sata)
56x cd rom drive(IDE)
52x cd burner(IDE)
floppy
T.R.U.E. cpu heatsink
No overclocking done atm
Nvidia Geforce 8800GTS 512
Soundblaster X-Fi platinum

For some reason Ive been getting random restarts and freezes and I wanna know where to start troubleshooting. All the stuff in there is new except for the hard drive. Ive had it about 3-4 years now. That and the cd rom drives. The vid card, psu, cpu, ram, board, those are all fairly new. Bought them in January. Can anyone point me in the right direction? I know I have two drives in there, both 74gb raptors, and I had to have one RMA'd and when it came in I installed windows on it and left the one I am on now alone because I had a new drive. Well the pc started freezing and restarting randomly(about once or twice a night) and it finally had an error and Id have to reinstall, so I plugged the old one back in and im on it now, and im still gettin random restarts and its bugging the crap out of me. Ive also ran memtest86 over night with no errors at all. Ive set windows to not restart upon an error and it does anyway. The screen goes black and turns off and right back on, none of the fans wind down or hard drives or anything.

[GSKILL TECH]

remove one of the memory and see any problem or not
make sure you have enough voltage for memory

[Jayfaas]

Ive removed one at a time and it still does it.

[GSKILL TECH]

Ive removed one at a time and it still does it.

both memory modules are bad, the chance to have this issue is very low. make sure your other hardware is ok.
if you need rma, please fill out the rma form and return to rma@gskill.com

[Jayfaas]

Any possibility that it could be the mobo or PSU? Ive also had the problem where Ill come in the room and hit the button and nothing will happen, and I have to switch the switch off on the back of the PSU and then back on to get it to cut on, and even sometimes when I do that ill fire it up and all the fans will come on, but it never posts, so the fans just stay running real fast. Any ideas?

[Jayfaas]

Would it maybe be the motherboard? What are some things I could do to take that out of the equation?

[HuffPCair]

Well it could be about anything. Have you error tested your hard drives and see if you have a bad sector or something.

[Jayfaas]

all ive done so far is memtest. Im hoping that its not the PSU but I dont really know how to test that. Ive heard and thought myself that it is probably the PSU but then it could also be the motherboard but ive had the motherboard and the PSU the same time so I dont know. Is there a way to rule out the mobo or psu with a software test?

[Jayfaas]

actually I did one day. It was a free program that puts a load on the hard drive, and I did and it ran the test and came back with no problems.

[Jayfaas]

Any other ideas? Its getting progressively worse and I really need to get rid of it cuz it gets me in the worst times in my games. I play cs and WoW and it'll get me during a match or right in the middle of a naxx raid or something. Please what are some ways I can rule out the PSU and mobo/cpu?