If its a Gen 1 pci express x16 slot then no, you cannot run a 2.1 card on it. For that you will require a pci express x16 2.0 slot. You can look towards getting a Nvidia GTS 450 though. It is a 2.0 card which is backward compatible with 1.0 slot. And don't worry, there will be no performance hit. In other words, you will get the same level of performance.