%APPDATA%\ICQ\
there are many many confusing folders & files
seems that every icq account has an own file-cache (for recived files from other users) and an own history
also there are many crap-files from updates, xtraz..
yeah i know i could make it with the "Winapp2.ini" if i had the time, but i think there are soo many people using ICQ AND CCleaner that should be a standard function..
ps: i have icq 7