Probably a silly question, how do you install video drivers with 2 cards

When you have 2 video card's, one's nVidia the second a xFx, both are installed and running perfectly, and when doing a full format & OS reinstall, are the driver's from the xFx installation CD going to be all it needs to run both video cards, I don't need to use each video card's driver CD, that would be like installing one over the other. I know the video card's must be identical, just one is nVidia and the second is xFx 

H.G.

XPS 730, Q9550 2.8GHz, 1333FSB, 4GB DDR3 1333MHz, 1GB nVidia GeForce GTX 280 + 1GB xFx GeForce GTX 280 -  790i Ultra SLI, twin WD velociraptors 150GB 10K, 32bit Vista Home Premium, LG Super Multi Blue + liteon/dell blue-ray drives, Dell 19 in 1 media reader w/Bluetooth 2.0, X-Fi sound XtremeGamer Fatal1ty Pro, Logitech z5500 5.1, SONY KDL-52"W3000 Monitor/TV