Repair.exe

[Henhouse]

If you have an external hard drive or enough disk space on your computer, make a copy. Or copy WoW.exe, the Data folder and Repair.exe and that'll usually guarantee that it will restore.

[Primez]

...make sure you change the:

set patchlist us.version.worldofwarcraft.com

to:

set patchlist smolderforge.dyndns.info

Or to further ensure that your game doesn't patch, remove the "set patchlist" line completely.