An update: Running MAME titles in a window with D3D still causes the PC to reset. Running MAME (either mame or mameUI) from teh command line using the switches mentioned also still cause it to reset my PC. The only option I have is to run in DDraw mode. This issue is happening outside of GameEx so I shall go track down a MAME tester and log the fault with them. I was hoping someone might have come across this before but it seems to not be the case. Running other emulators is fine (RAINE, KFusion, Snex9X, Daphne, MESS etc) as is running 3DMark 2001 SE (score of just under 8000). It's a weird one but for now I will live with the blurry nature of the DDraw mode. Thanks guys. M