My 6850 fan broke so I replaced it with my old 4850.
I have done the proper driver removal tools(driversweeper in safe mode etc) and installed the 4850.
Other games all work fine except for D3.
When I launch D3, the screen turns black and my whole computer crashes. It reboots on itself in 15 seconds.
I've tried deleting the d3pref.txt file as well.
Any idea on what else I can do to solve this other than a complete reformat?