MUSHRAN, welcome to the Seven Forums.
AGP video card
drivers will not install or work properly without a work AGP/GART
driver (part of the chipset), that is also why you had no problems with it in XP. You have to remember with the exception of the video card, the motherboard and likely the CPU probably came out even before XP did.
Now with that said go here,
http://w3.sis.com/download/download_step1.php?id=155871
and down load the SiS AGP/GART
driver. Before installing check in Programs and Features and if the ATI
driver is showing, uninstall it. Now install the AGP driver likely needing to use compatibility mode to get it to install,
Compatibility Mode
Once installed run Windows Update and there should be an update showing for the AGP driver, if there is install it. Now you should be able to install the driver for the card,
AMD Catalyst