I bought a new Gateway GT5408 and added a PNY nVidia 7600 GS 512 MB video card. I used a Chiefmax ATX Switching Power Supply (550W) to run the card. Now, here's my problem: Every time I try to play a game with higher-end graphics, like Obliivion or Sims 2, my graphics card will freeze up. I will get little lines in the picture, the picture freezes, and eventually, the card just shuts down. My monitor will go off and I will be left with no other option than to turn off the computer and restart it. I have contacted PNY (a test of patience in and of itself) and they seem to think the card is faulty. Since it was much easier to do so, I returned the graphics card to where I bought it and got another one. It does the exact same thing. I have downloaded the newest drivers, so that's not the problem. Could I have another faulty card, or is it possibly an issue with the type of power supply I got? I'm frustrated as I can get. Can someone please advise me as to what the problem could be?