how did you add them in in the firstplace!!??!! there are two ways of doing it. The first is FILE, OPEN OTHER USERS FOLDER. This will open up another window. The second method is to open up services, exchange server and under the ADVANCED tab, add the user account in.
When you have finished (depending on how they have been set up initially), either close the window or go back into services, exchange server, ADVANCED and remove the additional mailboxes.
doe this help?