Windows 7 PC with a "PCIe 3.0 x16 slot" (Carterton OX18)

On the lookout for a working Windows 7 PC with a "PCIe 3.0 x16" slot.
Not fussed about the state of the case, just needs to be working.
So it will be a PC that is about 10 -12 or so years old.

Thanks