Custom Computer

I have been fixing computers a lot, but when I can to this computer, I have a problem.
Lets start from when I reinstalled windows xp. After I reinstalled it, I had no idea what drivers they had for the Ethernet Controler, Video Drive, and PCI. When I called them to find out, they didn’t even know what drivers are. SO is there any way I can find out what hardware there are using and install proper drivers? Thanks N.Kotov