Cannot Boot with Quadro 4000 Cannot get past Grey Screen


I cannot get past the grey screen of death with the Quadro 4000 installed.

Here are my speca: Mac Pro(Intel Dual Quad Core), 4 GB of RAM, OSX 10.5.8 (before Snow Leopard).

My old Nvidia GeForce card died and so I was recommended by my authorized Apple re-seller to purchase the Nvidia PNY Quadro 4000 because I am a video editor and I utilize the Adobe Suite and Final Cut Studio daily. Awesome.

I installed an attempted to run the new video card with no luck. Finally, after much troubleshooting I took it in to the Apple store where they were able to boot my computer and run it fine with another card. Ok, so then I knew it WAS the card and not the motherboard, etc. I assumed that the Quadro 4000 was DOA so I exchanged it for a new one which arrived today from Amazon (Yes, it says “for mac” on the side of it). I just installed the card and still no luck. I understand that I need Snow Leopard to be able to run the card but when I choose my start-up volume by holding the ‘option’ key and choose the 'Mac OS X Install Disc or my usual start-up HDD I just get the grey screen which infinitely loads for a few minutes before the multilingual screen telling me that “I need to restart my computer” drops down.

I have been searching various forums for the answer but I cannot seem to find an answer as to how to get the OS X to install Snow Leopard or allow me to get past the grey screen to my desktop. It seems as though most people are able to start-up fine and just have other issues.

What’s funny is that if I choose WINDOWS for the start-up disk…it works…

Do I need to get a video card that works, install Snow Leopard, download the drivers for the Quadro 4000 and install THEN put in the Quadro 4000? This is the only solution that I can think of.

Any help would be much appreciated.

Thanks in advance.