my computer randomly restarts first it was just in games but its worse now ive been trying for a while now to sort this problem out but nothing has worked so far.ive tried .swapping cpu .formatting hdd and reinstalling the operating system .using windows xp home edition .swapping psu .swapping ram .cleaning the registry .updating drivers and bios .buying a better cpu fan but nothing has worked I also tried using ubuntu by booting it off the disk i left it on for 6 hours and it did not restart. any help would be aprreciated also i have never tried to overclock heres my specs operating system: windows vista home premium 32 bit graphics card:XFX Nvidia 8800GTS 650M 512MB DDR3 PCI Express graphics card ram:corsair xms2 2x1gb modules motherboard: gigabyte n650-sli ds4l psu: corsair TX750w hdd: maxtor 320gb sata2 7200rpm cpu: core 2 quad q6600 2.4ghz

Are you sure that nothing is overheating. Its most likely your motherboard or something isn't compatible with your motherboard that's connected. Something could be wrong inside the case. Open it up and look at everything and make sure everything looks right and is connected right.

im sure that nothing is overheating because that was one of the first things i checked the graphics card stays in between 50-53 and the cpu around 30 when idle and nothing is obstructing airflow in my case also the random restarts sometimes happen in the first 2-3 mins of the pc being used. i had a look in my pc to double check if everything was connected correctly and everything seems fine.

also it randomly restarted using windows vista and the same with windows xp but when i used ubuntu booting off the live disk (not hdd)i left it on for over six hours and there wasnt a single restart or crash.

simmo, I did some googling & ran across several reports about the 650i northbridge chipset running very hot, especially if it's passively cooled (i.e., heatsink only, no fan). If you have a room fan you can use, try removing the side panel & placing the fan so that it blows into the case, then see if the reboots continue. "If my answers frighten you then you should cease asking scary questions" - Jules Winnfield (Samuel L. Jackson) in Pulp Fiction

i removed the side pannel found a room fan put it on high and all the fans inside my antec 900 case i put on high as well and as soon as call of duty 4 demo loaded it restarted

A couple of things to look at. First, check the BIOS settings for RAM voltage and timing. Then read the sticker on a module to see if your settings are correct. Most OCZ RAM requires more voltage than the default MBoard settings. This should be addressed by the SPD on the modules but worth a look. Next, your Graphics card is one item that hasn't changed. I know you stated you reinstalled WinXP and updated the drivers. Are you using the Windows GART driver or the NVIDIA one? Your board specs mention a "North Bridge fan connector". Are you making that connection from the PSU to the board? I would try using some of the Nvidia tuning tools available. Below are some links. http://downloads.guru3d.com/downloa... http://us.download.nvidia.com/Windo... http://www.nvidia.com/object/winvis...