Hi there, could you give a little more detail for us?
How many monitors are you trying to use?
What OS are you running?
Are you sure the second card isn't being recognised once you have booted into your OS?
If you are trying to get your monitors to show at boot and only one is, that's pretty normal. Multi monitor mode works from within the software environment. With ATI cards, Crossfire Mode is enabled by default and to get more than one monitor working this has to be disabled first.
Assuming you are using Windows and that you have the ATI Catalyst drivers installed and that BOTH cards are being recognised in Device Manager. Right click on the desktop and go to the Catalyst Control Centre Panel. In the top left corner of the Pop-up panel is a drop down menu with the heading Graphics. Click on this and then click on the bottom heading which is for Crossfire. Untick the box and hit the apply box. Your screen will flash for several seconds as the driver re-sets itself. Then you will be able to run multi monitors..