It usually works better to do as Disk Contented said...identify all the hardware and download the drivers before you format, burn them all to a CD. You only need to do that if you don't have the driver CDs that came with the computer, though.
If you don't know what all the hardware is (video card, sound card, modem, network card, etc.), download, install and run either
Everest Home Edition or
Belarc Advisor. Both are free and both will inventory your computer and tell you the make and model of the hardware components. With that information, you download the drivers from the various component manufacturers.