you shouldve recieved a CD with it, unless you already used that, then a common mistake is that you didnt connect the card to the power supply (usual req for 8+ pipeline cards) then try the CD again and then if it still doesnt work try "Add new Hardware" in your Control panel.
... WOW, but he is using AGP card so unless someone buys him an SLI board... meh. BUT THERE IS A SOLUTION!