its not the cards...I am running the ati 4850's and one card is automatically disabled (just upgraded from xp to 7) I am trying to figure out how to enable the 2nd card.
if you go into the information center of the ATI user interface you will almost certainly see that one card is disabled, this indicates that the machine sees it, but the software has not turned it on...if I get mine all Ill post the solution.
Did you ever figure this out? I am having the same problem. Need Help.