If you preveusly owned a 5800 card it's likeley to be some old registry entries remaining, try uninstalling the ATI drivers in control panel, Run CCleaner Registry clean (or find a guide on how to compleatly remove AMD/ATI drivers is eaven better), and reinstall CCC.
I did tried uninstall the ATI driver then use driver sweeper to clean the leftover files and reinstall the driver again but it still can't detect correctly. At the mean time GPU-Z & Catalyst showed correct information. weird thing...
I am having the same issue but it is detecting a 4800 series video card instead. I did previously own a HD 4870 but i have removed the drivers properly and every other game detects my new video card.
I spoke with Beth support and they told me to contact my hardware vendor and since the steam patch the work around i was using doesn't so good stuff all round.
If the performance is better than your old graphic card. And if the performance is it's suppose to be, why do you care about what it detects? You want to show it off or what? Lol. Why don't you leave it? It will be ok if you leave this.
It's just because I'm not sure whether it should have this performance in Skyrim. Anyway I had already fixed this issue by re-install the whole Windows system then it detect 6900 series correctly. Thanks for you guys' help. Good luck.