I've seen systems reboot and still leave a minidump to diagnose. You can use something like WinDbg to hopefully see what module is causing the crash - maybe video drivers... which might not solve anything, but at least you'd know. http://www.techradar.com/news/computing/how-to-diagnose-and-fix-blue-screen-crashes-595800
I don't know what caused my computer to reboot but since reinstalling and not registering my game is now stable. I wish I knew what was the problem as it is gone now. I checked up and down the event viewer of windows 7 and nothing. I have not got the problem since I fist had it and did not change anything so who knows what caused it. :(
Maybe other people can try do what I did. Uninstall the game, go to my computer and delete the folders there, go into the registry and delete all entries for cdproject and gog and reboot. After rebooting install the game again and not register and see if it happens again. I also used ccleaner to clean all entries in the registry and temp files.
I am worried about registering since gog did not come back to me why registering the game makes The Witcher 2 forget I have the gog version and not the disc version. This seems to have been my problem. I did my steps above and no problem now.