Playing both WOTLK and CATA

Love what warmane does and I consider it one of the higher end private servers. With that in mind, is there a way I can play both Cataclysm and Wrath of the lich king on the same computer? I currently have wotlk installed, would installing cataclysm screw with my wotlk install? i'd ideally like to have two seperate folders to launch from, one for wotlk and one for cata, but i don't want to waste the bandwith if it'll screw up one or both versions. any input is appreciated, thanks.

Installing new expansion will not mess around with your previous one as long as you have them in separate folders.