I have a Dell XPS 600 system running Windows XP. I was running two Nvidia 6800's in SLI mode and decided to upgrade those video cards. I purchased two 9800GT's and put them in the system in place of the 6800's. During replacement, I uninstalled the 6800 drivers, replaced the cards and installed the 9800 drivers. After installation, one of the video cards appeared not to be operating within the system. In Device Manager, both cards are shown installed but one has an exclamation mark

I tried removing all PCI cards except for one 9800 and re-installing each card seperately. I had removed the second 9800, my sound card and an IDE control card. When I put in the second 9800 card, I encountered the same error. Windows didn't assign different resources. Not sure if it matters but I noticed both cards are set up under IRQ16. I wanted to try and manually change the resources for the second card but the option to change settings under the Resources Tab is grayed out and the "use automatic settings" box is checked.
I have the latest BIOS version Dell offers for this system. I've seen some posts with users having this problem running Windows 7 so not sure if XP is the problem. I'm not sure what to do at this point? If the second card needs different resource settings, how do I get Windows to assign them correctly or allow me to change the current settings? If my previous cards worked in SLI with available Windows resources, how come Windows is having problems with replacement cards?
Thanks for any help on this!!