cant get it to work

When the PC loads up it says using PCI gen2 and then under it it says no device found
And when I try to install an old copy of windows xp it blue screens and says an error with PCI something
I have an his 7950 and a ASrock pro4

Did you check to make sure the cards seated right in the slot and the extra power connectors were plugged in?

When you said you tried an old copy of XP, was this a clean install?

Any chance you can try the card in another computer?