afaik the only AGP card that runs in a Mac and a PC right out of the box is some retail radeon 9600 that had ROMs that worked with OF and a BIOS. all other cards have to be flashed or wont work at all due to the magic apple added to their agp slots.

the 24v should be the small extra pin next to the agp slot that is just missing on PC boards so the card shouldnt be physically damaged when put into a pc.