Hello Fellow Simmers, I'm looking at giving my PC a mid-term upgrade. I can get an Athlon 64 3500 (Winchester Core), Socket 939 Mobo, 1GB 400DDR memory and a new 80Gig HDD for

Stan,Go for a 500w and you'll be good to go for a while, just be sure you get a quality brand with steady rails 12v, 3v etc.