PC restarts without BSOD

[Zdravets]

The problems started when I installed a new video card to my PC - GeForce GTX 770. I bought a new power supply for it, as I remember some Corsair 600W silver. The following problems started: firstly windows loads normaly, until the sign up screen appears. Then it starts to flicker very fast. A second after I write my password and click enter, the screen stops to flicker and windows loads normaly. The main problem is that windows restarts appr. 10 min after loading, withouth any BSOD msg. I've updated all drivers, repaired registries, checked for viruses - nothing helps. My previous videocard was radeon 7850. Is it possible, although I uninstalled the old drivers, they still mess up with my nvidia ones?
Please help, before I reinstall windows

 

[190221]

sounds like your card or psu might be bad. did you try putting the old video card back in to test?

 

[Zdravets]

No, because it was damaged, that's why I replaced it with a new one. I might try this though. Strange thing is that I played Diablo for 5 hours without a single restart. But when I just stayed in windows with a browser open, it restarted 6 times for 2 hours...