Open a Terminal session and do this
sudo /Developer/Library/uninstall-devtools --mode=all
If you try to get the non-beta version, it now redirect you to the Mac App Store, telling you that it is a free download now. So download that. Half an hour later, click the new app called “Install Xcode”
If iTunes is running it will ask you to quit it. If you quit iTunes and Xcode does not continue installation, that is because iTunesHelper is still running. Open Activity Monitor and Force Quit iTunesHelper.
- If Simulator is running, remember to quit that first.
- If you are installing an earlier version of Xcode, reboot after installing. If not Xcode will keep crashing on launch.