Help with random freezes / restarts

[Dnx]

Hi guys, I've got a problem on my pc that started like a month ago orso, I got random freezes / restarts, what I have noticed is that it always happends on the first lets say about 5 minutes after I log onto my windows account the funny thing is after those minutes if it stays normal it stays normal for the rest of the day if it remains on, I have alredy tried registry cleaners, RAM windows tests, I ran the tools to attempt to find and fix hard drive errors, and ran a full antispyware and it did not worked, im running windows 7, my cpu its an i7 920, 8gb of ram, gtx 670, I have read that it might be problem of the PSU if its bad quality or if it does not have enough wattage, but I have a corsair 650w txm, that I bought at the end of last year along with the video card so I really don't think that's the problem, I think my mobo its dying, does any1 thinks the same? or what else could it be? thank you.

 

[Guest]

try to re install windows (clean installation)
monitor your fan inside pc.