[Update]: It's been figured out. Long story short: I purchased a 5850 card, installed it into my Windows 7 x64 rig and ran the Windows Experience Index and found the score was stuck at 6.0.
After EasterEEL discovered the problem and a solution, I brought the score up to 7.7.
So, to solve this problem: Set your "standard settings" slider in Catalyst to "balanced" and you're set!
Long story...:
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Hey guys, new to the forum, been watching and reading the site for about 2 months now.
So... by a stoke of pure luck, I found and purchased an HIS Radeon 5850 at Memory Express in Calgary yesterday. Thanks to an MSDN subscription, I also have the Windows 7 Ultimate RTM. So, with both of those installed, I did what any normal person who cares to see what Microsoft has to say about your computer would do and I ran the Windows Experience Index.
Things were sort of as expected. My CPU and memory are between 7.5 and 7.9 respectively. And my 500 GB Seagate HDD comes in at 5.9. However, what really baffled me was when I saw the score for the graphics. Both scores show up at... 6.0.
What?

I have the latest driver from AMD (released Sept 21st) and my old 3850 which I replaced had a score of 6.1. Now, I know, I know. The WEI is useless for real benchmarking. I don't care. I wanted to see at least 6.6-7.1 or something. I'm annoyed.
Any ideas as to what is going on here? Anyone with 5870s that has been tested with WEI that are getting similar results?
Cheers
http://img27.imageshack.us/img27/5352/weix.jpg