If you're hurting for space, also check your World of Warcraft folder. It seems WoW doesn't remove old patches, so you can safely erase any folder that references an older patch number, like 1.11 to 1.12.
Edit: Installers and downloaders for those older versions will be in the main WoW directory also, you can delete those too. Just make sure to leave wow-patch (no numbers) and anything that lists patch 2.0 or higher!
Edited, Dec 5th 2006 4:13pm by Krylanna