In the ref log I'm finding a surprising number of search phrases regarding the uninstallation of Service Pack 2. It's not on the add/remove programs list unless you check the box labled Show updates. After you check this box it'll be under Windows XP - Software Updates. This picture says it all :)

After clicking on remove you'll be shown a list of programs you've installed since installing SP2. It basically tells you that they may not work properly after removing SP2. I personally didn't have any issues with the programs after doing this but make sure you have the install disks on stand by JUST in case. You'll also need to uninstall RC1 before you install RC2 which should be released sometime in May.