Downgrade to 3.3.5

After you downgrade, run WoW.exe(windows) or World of Warcraft(mac). NEVER RUN THE LAUNCHER.
Guide updated as of July 24, 2011 and should be working if you did it correctly.

Step 1: Uninstall World of Warcraft.
Windows: Go to your control panels and open Add or Remove Programs. Once that opens, locate World of Warcraft and click the remove button.
Mac: Move the World of Warcraft folder to the trash, and remove Users/Shared/Blizzard to the trash, then empty the trash.

Step 2: Install World of Warcraft and all the expansions, but DON'T PATCH UP YET
*When they are done downloading & installing the launcher will open automatically, close out of it before it automatically updates patches.
*If you don't get ALL of the expansions before this guide, it will not work.
Windows: Run the disk to install the original World of Warcraft, or download & run InstallWoW(Windows), select "World of Warcraft" from the scroll-down list, and click "install"
Mac: Run the disk to install the original World of Warcraft or download & run InstallWoW(Mac), select "World of Warcraft" from the scroll-down list, and click "install"

Step 3: Manually install the World of Warcraft patches
*If you don't manually install the patches, it will not work.
*To manually install patches, download the file, drag it into your World of Warcraft folder, and launch it.
*After it's done updating, the launcher will open automatically. Close it QUICK before it starts updating patches automatically.
*You have to download & install the patches in order.
*On macs, you have to unzip the file before placing it into your World of Warcraft folder (you can do so by double clicking on the .zip folder)
All Windows Patches:
x.x to 2.4.0
2.4.0 to 2.4.1
2.4.1 to 2.4.2
2.4.2 to 2.4.3
2.4.3 to 3.0.1
3.0.1 to 3.2.0
3.2.0 to 3.2.0a
3.2.0a to 3.2.2
3.2.2 to 3.2.2a
3.2.2a to 3.3.0
3.3.0 to 3.3.0a
3.3.0a to 3.3.2
3.3.2 to 3.3.3
3.3.3 to 3.3.3a
3.3.3a to 3.3.5
3.3.5 to 3.3.5a
All Mac Patches:
x.x to 2.3.0
2.3.0 to 2.3.2
2.3.2 to 2.3.3
2.3.3 to 2.4.0
2.4.0 to 2.4.1
2.4.1 to 2.4.2
2.4.2 to 2.4.3
2.4.3 to 3.0.1
3.0.1 to 3.0.2
3.0.2 to 3.0.3
3.0.3 to 3.0.8
3.0.8 to 3.0.8a
3.0.8a to 3.0.9
3.0.9 to 3.1.0
3.1.0 to 3.1.1
3.1.1 to 3.1.1a
3.1.1a to 3.1.2
3.1.2 to 3.1.3
3.1.3 to 3.2.0
3.2.0 to 3.2.0a
3.2.0a to 3.2.2
3.2.2 to 3.2.2a
3.2.2a to 3.3
3.3 to 3.3a
3.3a to 3.3.2
3.3.2 to 3.3.3
3.3.3 to 3.3.3a
3.3.3a to 3.3.5
3.3.5 to 3.3.5a

Enjoy playing on private servers again

*If you want to play retail, download World of Warcraft as you normally would and just put it in a different location, therefore you have a version 3.3.5a for private servers, and a version 4.0.1+ for retail.