I added a hard drive to my computer a while back and started running into some hardware issues. I have a 500w power supply. It's powering a 2.2GHz Athlon 64, four hard drives (2 SATA, 2 IDE), 2GB DDR2 RAM, and an ATI x1950 Pro. When I added the fourth drive, I started getting artifacting with my video card -- green pixels flicker randomly on the screen at all times (on both of my monitors, so I know it isn't a monitor issue), and there's obvious problems in any 3D games (like random vertices stretching off to infinity).
Did I reach the limit of my power supply, or is it possible that my video card is just on its last legs? I'm actually thinking of adding a fifth drive soon -- should I bump my power supply to 750w just to be safe, or is that completely overkill?