go to wow folder, drag your wow-64.exe to your desktop, create shortcut on desktop to wow.exe, click on new shortcut, viola.
If you're launching through b.net app, go to settings and make sure launch 32 is checked under game settings.
From my experience, you can't just delete wow-64.exe or the b.net app will just re-create it when it launches again. You have to actually move the wow-64.exe file somewhere else.