When you upgraded did you use the "upgrade" feature or did you install a clean version of Win7? If you took the upgrade path you should uninstall those drivers first.
When you look at device manager does it show the second card or is it missing/yellow bang?
I think you will be fine if you uninstall the drivers and reinstall. If that doesnt work, uninstall them again and remove your second crossfire card and reinstall. Turn off and add the second card back in. You may have to reinstall the drivers again - dont let Win 7 do this for you. Say skip or Cancel and rerun your drivers.
If that stll doesnt work uninstall, go into safe mode and use one of the registry cleaners for ATI drivers. One of the problems we run into is System Restore keeps track of the versions of files and sometimes tryd to reinstall and older driver. I have had to turn off System Restore in order to remove old hardware drivers.
UPDATE: I contacted ASUS motherboard manufacturer. I was told that the Crossfire/ATI/AMD is not designed for the board and will never work. I contacted my unnamed company (VELOCITYMICRO) and was informed that they do indeed work and the company has a special driver....follow the link. I did; it is dead. I informed the company that the link was dead..........It is still dead. January 19+/- on. A tech support rep has assured me that the drivers will be placed on a cd and sent to me. Now the company did not know this computer needed special drivers? It was not shipped with these drivers, the tech support people did not know about these drivers, there is no mention on their web site of anything about these drivers....the link to the drivers is s dead end? You think something is up?