Well you have a decent configaration, D3 requires extreamly powerful graphic card, you can't possibly think you can runthat game in High Q on a GeForce 4! froms the looks of it, i think your using a GeForce FX 5200, the reason mustbe you running the game in a very high Quality mode, thats why thegame come backs to the desktop, run game on Medium 800x600 resolution with AA and AF turned off. and shadows and bump mapping setted to a very low level, the probshud end, also make sure you Pc isn't overheating, some times when processors get to hot, they start to behave very erratic, make sure if yor CPU is getting enough air, and the PSU your using has enough power(atleast 300W on that config) so go and do it!