I have a problem changing Graphics Cards from Mac to PC

[spideropt]

ok here is the problem i have a 400mhz mac wiht a 128pro Ati redeon.
I have a PC 1.80 ghz with a nvdia 64 mb card. i changed the Ati to my pc and the nvidia 64mb to my mac and i turned on my Mac and the screen didn't turn on. ok I only have one screen the i use for both. so i connect the mac screen to my pc and it did'nt turn on why???

[Beefy]

Not a good idea. Although they look the same, there's a couple differences in some of the Mac cards. The main one being that some of them actually supply power through the card to power the screen (mainly for DVI LCD screens). Also, the DVI connector is slightly different to incorporate this.

Mixing MAC and PC video cards is most definitely not recommended for this reason.

[Lava Lamp Freak]

The old card he is using would just have a VGA connector. But the Mac and PC cards have different firmware. You can't just move them between computers.