Adobe has posted a Windows cleanup script (alongside the equivalent Mac version) that removes vestiges of the Photoshop CS3 beta as well as other Adobe pre-release software. If you’re having trouble installing Photoshop CS3 or other new Adobe apps, this script may help. You may also want to consult the tech notes on removing the PS beta on Windows XP, Vista, and Mac OS X.
The download page warns of nuclear holocaust, rivers of blood, etc. resulting from the use of the script. I think the team is just being extremely conservative and cautious, but I believe there is a chance that the script will remove serial number info for Acrobat 8 (meaning you’ll need to re-enter your serial/reactivate).
One specific point: A number of people have asked whether it’s strictly necessary to deactivate the beta prior to uninstalling it and installing the shipping version. Deactivation is accomplished via the Help menu, so it’s obviously a problem if you’ve already uninstalled the app. The good news is that although deactivating is a good idea, it doesn’t seem to be necessary prior to installing the shipping version.
All this stuff can be pretty tweaky and system-specific, so please let us know if you run into problems. Chances are I don’t know the answers myself, but I can route info back to the right people as necessary.