NFS World crashes and PC restarts automatically

Some driver is failing. Disconnecting unnecessary hardware might get it to run a bit longer, then let you add stuff back one at a time. Try unplugging all printers and things like that, close any background programs like MSN and uTorrent while you play games and see if that improves your situation.

If not you could strip out MSCONFIG and uninstall any applications you don't use anymore, so there is less running when you're playing games.

You could also try reinstalling Windows if you're certain this isn't a heat related problem, and see if that fixes it.

Turns Out that the GPU has molten (Yet it was working !!!) , I replaced the GPU , then changed the MB and RAMs, games are now playing wonderfully and everything went back to normal.