HOW TO DOWN-PATCH

1. Go to your World of Warcraft folder, usually C:/program files/world of warcraft/
2. Find the Data folder
3. Go into ->enus->engb folder
4. Find and remove 'patch-enus.mpq'/'patch-engb.mpq'
5. Open up repair.exe in your main world of warcraft directory
6. Uncheck all check boxes and click the 'check files only'button
7. You have to let the repair run all the way to the end
8. You should be now at version 3.0.0
You have two options here:
9a. You can use the world of warcraft launcher (launcher.exe in your main /world of warcraft/ folder), or
9b. Download the patches manually from from a website such as Patch mirrors - WoWWiki - Your guide to the World of Warcraft.
10a. Launcher option. Open up the launcher and click play. Then type in
any garbage login info, and it will start patching you up. Keep doing
this until you have patched to 3.0.9.
10b. Download the patch(es) you want (make sure you have the right
language version), and stick them into your world of warcraft folder
and run the patches.
12. Use wow.exe from now on to play the game. (Launcher.exe resets realmlist to retail).
13. Don't forget to change your realm.


Not made by me, found it