We'll need more info. What are the rest of your system's specs? Judging from how old your platform is, I'm assuming your PSU is also as old or possibly not a suitable candidate for a new card.
Apart from that, your board will also be on
PCI-e v1.1. Why that will be a problem is that v1.1a wouldn't allow for PCI-e 2.0 cards to work properly while slots of PCI-e v1.1b allowed for cards with PCI-e 2.0 to be backwards compatible.