"The 13.1 driver does not support Tahiti LE. It was an error when the driver was compiled. We've re-added support and re-submitted the driver to Microsoft so they can re-certify the driver with Tahiti LE added to the .INF file.
You can either force-install 13.1 onto your card as the 7900 Series, or you can use 12.11beta11, which is virtually identical. The driver should be back from Microsoft and uploaded this upcoming week.
We would've done it Friday, but any time you make any change to the driver that's received WHQL, it has to go back for testing. Yes, even if it's just a change to a text file."
Une réponse sur un autre forum très intéressant ^^