Remove the old haunted version from the UTGamepublishedCookedPC folder and delete the UtHauntedGame.ini from UtGameconfig
Extract the contents of the rar file into your DocumentsMyGamesUnreal Tournament 3 folder
Now you can launch the haunted or the editor with the shortcuts.
The shortcuts will try to find your UT3.exe first.
Right click -> properties to locate it manually.