It’s almost RTM time, and that means the beta has to go. Unlike previous beta debacles, this one is actually pretty easy. If you run the RTM install, you’ll get a list of software you need to remove. Ignore the list—you only need to remove one item, and it will daisy-chain the rest of the software.
All you need to remove is Microsoft Windows Phone Developer Tools Beta – ENU.
A reboot is required once the uninstall has completed, so be prepared. The uninstall takes 10-15 min, I wasn’t paying very close attention.
More information at http://blogs.msdn.com/b/jaimer/archive/2010/07/13/tips-for-uninstalling-the-windows-phone-developer-tools-ctps-and-moving-to-beta.aspx. Although written for the CTP, it works the same for the beta.