Freshly reinstalled Win 7 Ultimate X64 keeps freezing up

[Kmerse]

I'm wrestling with this issue for a week now, since I decide to format my hard drive and reinstall my Win 7 Ultimate X64.
I'm using my computer and out of nowhere it suddenly slows down drastically and finally freezes, nothing helps but hitting the reset button.
Interestingly it never happens during watching videos or playing video games, only when I browse or I try to return to Windows. I'm still looking for the pattern in the error.
I checked the event log, I saw a few error messages with the graphics drive, I have read that the latest version is unstable so I reverted to a previous version, which was said stable, but it didn't solve the issue. Nor did turning off hardware acceleration in Firefox (the issue didn't appear exclusively during browsing anyway).
Currently I'm stuck. The event log doesn't tell anything useful for me any more, so I'm turning to the experts here, maybe they can solve my issue.

Thanks in advance!

p.s.: I should add that my previous installation worked fine but it was several years old, slow to boot up etc. so I felt it's time to reinstall it. So hardware issues are most likely ruled out.

 

[Arc]

If there is no hardware issue .....

So hardware issues are most likely ruled out.

..... you should try another installation. May be this installation is not a perfect one. Follow http://www.sevenforums.com/tutorials/219487-clean-reinstall-factory-oem-windows-7-a.html.