Read all this talk about how the Radeon HD 5770 with work in a Mac Pro 1.1 so I picked one up from BestBuy. Put it in and my screens will not pick up a signal? It's installed correctly, has the extra power wires and nothing?

Mac OS X - 10.6.4
Processor - 2x2.66GHz Dual-Core Intel Xeon

If this is completely uncompatable, does anyone know of a good graphics card for my comp? Playing WoW and looking to get max settings on most, if not all of the video opions in-game.

Edit - Found a driver download, installed it with the stock graphics card in, then turned my computer off uplugged everything and put the new card in and still nothing(moniters didn't pick up any signal. Unplugged everything again and put the stock card back in and it will just sit at the loading screen? Tried to use the reboot disc and a bar on the loading screen will load half way then eject the disc one. So i put disc two in and the bar filled completely then it still sat at the loading screen. tried a restart and still sits at the loading screen. uhhh... anyone?

thank you,
Michael