My niece has just about the same setup on her Pc an E8400 Wolfsdale with a Sapphire 7770 she maxes out games on 1440x900 24" display.It will work in your Pci slot regardless but some people have a differing opinion when it comes to what PCI generation the board runs.
I don't think I've ever had an MB that ran over PCI 1.1 while nothing was running as long as it changes while running the render and doesn't change back before the render is closed it's probably fine.