and after tat, keep an install somewhere. a cleaned non modified, non modded untouched install. copy the whole folder someplace else (i have tons of diskspace, so i dont care) if you can spare the diskspace.
wow doesn't need to be "installed" you can run it from anywhere on any PC. you can take your wow on a USB disk to a friend and run it.
so, keep a copy. if anything goes wrong, copy back. saves you the hours of installation. ^^
Come and join on Starcraft 2 as well =]