That makes sense - and I was heading down that road. However, I have 2x 2 GB sticks with room for two more. Also, Memtest86 checks fine after at least 4 hours. The PSU is a Zumax 400W powering little more than a 350 IDE drive and the Video Card. I've loaded XP on this thing about six hours ago, and it's running flawlessly. What else should I be looking at? Keeping XP (which would be my first thought) is not an option since the individual that owns it needs it to link to a Linksys Media Extender, which requires the Vista operating system... which is the impetus for this problem. Try Windows in safe mode - does it hang there? If not, then it's a driver issue for sure. No, it doesn't hang in Safe Mode - so I'm looking hard at the video driver. However, There seems to be nothing I can do to make this card work, and it's supposed to be compatible with Vista. Using it's native drivers, or the drivers that came with Vista cause the same problem. I would suspect the card is bad if it didn't run fine under XP.