What Video Card is it?
There are quite a few important components that have to work with the GPU. Namely:
Motherboard (enough/correct expansion slots, also right amount of lanes)
Case (It's got to fit)
PSU (Got to be capable of delivering enough power, also you want decent brand)
OS[to some extent] Some OSs will only support certain CPU features, e.g. Windows XP supports only up to DirectX10.
Peripherals (You won't be able to take advantage of some features if you don't have them) e.g. Eyefinity on AMD cards, you need 3 monitors to utilise it