I play on a Mac, I assume Window should work the same. I patch my main WoW then copy the patch to my other WoW directories, launch them and let them patch. It sees that the patch is already there so it doesn't down load it again and patches those WOWs. I'm not sure why you would have to muck with the registry (worst OS feature ever).

Do any of you windows guys patch the way I do? Why doesn't it work?