Hey! Well, I decided to build myself a computer that's going to last me. I got a motherboard from a friend, I have an Orion 585w PSU, a Q6600 quad core @ 2.4gHz, and up until a few weeks ago, I was using an 8600 gt 256. I was having no issues whatsoever with that card. I just bought a Sapphire Radeon HD 4850, and suddenly my games do not work. They just crash my card and require a hard restart to fix. I managed to get the computer stable enough to run windows XP SP3 well enough, and I can still watch movies, go online, listen to music, look at pictures...etc. I just can't play games. The only exception to that is Garry's Mod. None of my other source games work, or any others, such as Crysis, Stalker Clear Sky, Rainbow Six Vegas 2, World in Conflict...not even the Hoyle Board games (my grandmother got it for me. Chess is fun, though haha) I've been told that my mobo is to blame, but I dont see how that could be if it worked fine before the card. I sent the card in for replacement from Newegg, but the new card still has the same issues. It was then suggested that it was the PSU, but I don't know how to test that. Any ideas? I havn't been able to use my computer the way I want to for like 2 weeks! Help me! Thanks!