Okay folks, here's a weird one that I'm sure more people will be asking soon.
I downloaded and installed the IE7 beta from MS's website, and it was running just fine. Then today, MS Update tells me I need to install IE7. I do, it runs for near half an hour updating itself, and then upon logging back in, my Internet Explorer installation looks and acts like 6.0, but the About dialog says it's 7.0. No tabs, no updated interface, just a 6.0 installation that thinks it's 7.0. No modifications were done to the browser.