Hello, I'm trying to install a Geforce 8800GTS but when I start my mac pro nothing happens, my display doesn't start and I can't select Windows in the Bootcamp. Anyway I tried starting Windows directly too and the same problem, my screen doesn't start. But if the DVI is connected in the ATI 2600XT and I enter in Windows I can see the 2 cards in the device manager, but my 8800GTS is marked with an yellow icon, saying that the drivers are not installed, but really are installed... I don't know if I'm doing something bad, this is my first Mac PD: I'm using an external PSU for my PCIe card, because I don't have a Apple PCI Express cable, but the graphic card works perfectly in another computer. Thanks and sorry for my bad english.