specify your cpu config., mainly your psu and graphics card, the graphics driver version, also tell that if you have ever seen "out of memory" error on a blue screen at restart.
also, specify your internet connection and tell that while watching internet video, what extra you download via torrent/ downloaders at that time.
also specify whether a particular site (give the name) is causing it or it is happening in all such sites.
and apart from all these, do check the temperatures of your cpu, graphics card and other current, voltage parameters by using some softwares which you will get for free by a search on Google,
a few such links are:
Real Temp - CPU temperature monitoring
Core Temp
EDIT: also, run in safe mode, If running in safe mode does not produce the problem that means that there is/are driver/drivers that is/are causing the problem when running in normal mode. These drivers are not loaded when you are running in safemode thus no problem occuring. Why not run your win 7 repair disk and go back to a a previuos date where your computer was running normally? Choose recovery (I mean restore) in the menu. Or if you can access recovery (system restore) while in safemode then do it.
EDIT 2: go to the bios>advanced>processor retest>enable(if processor retest is disabled), save and exit. It should solve your problem.