outlook 2010 exchange 2010

i have access to certain email boxes because im an administrator.
i added some and now i am trying to get rid of them but i cant.  the email boxes show up in the left pane of outlook.  I can't open the email boxes and i also can't disconnect or delete them through the advanced email account settings.  the reason i can't delete them is because they are not listed.
i know they  still there though because my ost grows to an enormous size.  49 gig on the local machine.  i only have 500 meg on the email server.

any ideas on how i can get rid of these previously used accounts that are showing up in my left side pane