CVar launchThirtyTwoBitClient

This CVar controls whether you use the 32bit or 64bit WoW client.

Default Setting

 * 1

Possible Settings

 * 0 :Open 64bit client on hitting Play on the Launcher
 * 1 :Open 32bit client on hitting Play on the Launcher

Changing this setting
In-game, type the following /console launchThirtyTwoBitClient setting

You can exit wow, open the Config.wtf file, and add the following line: SET launchThirtyTwoBitClient setting

Alternatively, you can open the Launcher, select Options, Game Preferences, and Check/uncheck the "Launch 32-bit client" checkbox.