My father gave me a GeForce 8800 GS video card today. I was overjoyed, since that meant that both of my primary desktops gets a discrete card. Unfortunately, things didn't work out so well.
First off, I put the card into Superflex, the primary desktop with an Athlon X2, and found out the card prevents it from POSTing. After discussing it with my father, I decided to put the 8600 back into the machine. Fortunately, it went back to the way it was before.
Paladin, the secondary desktop with a Phenom X4, wasn't so lucky. At first, I put the 8600 from Superflex in there, and it worked just fine without a hiccup. After I put the 8600 back into Superflex, I put the 8800 GS in there. It booted okay, and got to loading the kernel and starting init. However, when it came to udev's probing devices, the machine powered off, leaving the power light on. Even after taking the card out and switching it back to integrated (GeForce 6150) graphics, it still does the same, leaving me without Paladin.
I'm not sure what to do about this, but I suspect the power supply. Until I go out and buy one, there's nothing I can do.