I really don't know where to start.
Here is what I have: 
Intel Core i5-650 Clarkdale 3.2GHz LGA 1156 73W Dual-Core Desktop Processor 1011 Intel HD Graphics
G.SKILL Ripjaws Series 4GB (4 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 2021 12800)
EVGA P55 FTW 200 SLI 141-LF-E658-KR LGA 1156 Intel P55 ATX Intel Motherboard
(New Video Card) EVGA GTX 670 FTW
(Old Video Card) EVGA 012-P3-1470-AR GeForce GTX 470 (Fermi) 1280MB 320-bit GDDR5 PCI Express 2.0 
Western Digital VelociRaptor WD1500HLFS 150GB 10000 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive
Corsair 750 Power Supply
NZXT 810  case
(windows 7 64)
Ok so..... I have been having my computer Restart on me Randomly. Normally it restarts when I get open a Game (like BF3), but can also happen on start up as i sign into Windows.
I started with a Format re install. Didnt fix problem
next I pulled RAM out and checked all one by one eventually replacing it just in case, Didn't fix problem.
Checked the motherboard over very closely  nothing I could see.
Took my computer over to my "Computer guy" tried his power supply, Tried his video card when his video card was in (260) it seemed to not have problems so I ordered a new video card (I wanted one anyway) 
Placed new video card in and still had problems!!!!!!!!!!!!!!!
Gave him my old video card to run in his systems no problems there.... So I tried re seating my processor and still not fixed!!!
I am just looking for any advice on what my next steps should be.... May RMA the Motherboard but anything you guys could sugjest I would Try  So I stop going Thanks in Advance,
 
 Oh and its a Restart not a blue screen. (just like if I hit the power button)                                     

Makes me think PSU.

I've seen bad contact with the CPU fan and CPU cause that problem.  Sometimes bad thermal paste (or non at all) on the CPU/CPU Fan.  That PSU has a 5 year warranty and you can get a cheap tester for less that $20 to see if it is ok.  Check for BIOS update on the Motherboard?  Could be a known glitch?  Keep us posted!
 

I tried a new Power Supply and did not fix this problem.. Also pulled the CPU and fan out and reset it with new thermal paste  thanks for advice! but yes I already did these things.
 
 

So I have been experimenting... and I can surf the web and go over my excel stuff without causing the "restart" Problem. As soon as I watch a You tube video full screen or open up a game it causes the restart. This problem has been going on for  about a month now and with everything I have tried I can not figure out the problem. All I can come up with it hard ware. Question... Do you think there is anyway Possible that my Hard Drive could possibly cause this problem? Cuz if not I would say it has to be motherboard or CPU? I will just buy all new if need be just not looking forward to it, also want to make sure problem will go away if I replace anyway. FTW !

You used MEMTEST86+ for testing RAM?  Have you tried using CrystalDiskInfo to test your hard drive SMART status?  If it show "yellow" or "red" you can use WD DIAG for testing hard drive deeper.  Try setting all of your BIOS settings to default?
Typically motherboards and CPU's are pretty resilient.. when they go, you know it!  Did you see any caps bulging or leaking? (The little pop can looking things on the motherboard)

Yes I did use Memtest for the ram and still replaced it anyway  and ran again with new ram.
Also I have CrystalDiskInfo and its showing good health status on it. going over my motherboard I did not notice anything wrong It still looks Clean and Brand new looking Thank you but yeah I have done these things. Last time it crashed it did have a blue screen witch was nice to see something but it came up with no help searching on the web..... well nothing useful anyway . Thank you for the time man I do apretiate all of you guys for taking the time to help.

ive had my computer restart before, for me its because multiple settings were off: per overclocking guide. If your overclocked voltages might be off, any usefull info you can think of might help someone figure the problem out.

Yes. I do not over clock at all and I made sure Default was on in bios

I have RMA out on motherboard now. Also have new SSD drive Because i wanted one anyway. So the only thing that it could be is Motherboard or CPU at this point :/. ...  I just want my computer back together heh. Thanks all for the Addvice and what not. I will update when I get the motherboard back. I cant do much anyway.

I just went thru that looping restart junk. things to maybe help narrow it down would be to run the  everything out of the case rebooting one piece at a time. also monitor your temps and run prime 95.  you could have stock speeds(no O.C.) with a bad T.I.M.
I would also look at the gold contact dots on the cpu. Too much presure holding the heatsink down while you secure it or slightly move the cpu and you will create a bad chip to socket connection. There should only be one dimple in each gold dot. If there is 2 or more you may have some bent pins. Good luck 2 ya.

Thank you. Ill look into that.
 

OK so it was my motherboard after all. It looked like it had nothing wrong with it but RMA ing it  worked! EVGA rocks for there warranty!
I did take a little over a week  or so to get it all done but saved me from having to buy a new MB! Thanks EVGA!!!  
 
And thanks to the rest of you for your help also!

Man I was about to ask if you lived near me. I am glad you figured it out. Good job!

Thanks for updating your situation, it may help someone else. I would have bet on a PSU, because I have had that issue before. Glad you got it fixed.

Thank you! yes I was not sure myself but after all of the trouble shooting there could only be two things and I was afraid it might had been the cpu but all is better now thanks guys