Dell has a pretty good site for support and documentation. here is the link to their site with information about the specs: http://support.dell.com/support/edocs/systems/inspd530/en/OM/HTML/appendix.htm
From there you can see the computer supports PCI Express, but no mention of 2.0. A further search on their site reveals a question on their forum similar to yours:
In any event...you should be OK. The PCI Express 2.0 is backwards compatible with the PCI x16 1.0 and 1.1 slot motherboards. However, PCI-e 2.0 cards on 1.1 and 1.0 motherboards will not be able to run at their max capacity.
Thanks, also, one more question. Would this be ok for normal gaming? Not softcore or hardcore gaming, but in between?
and, could it run Arma II: Operation Arrowhead?