Exchange Mailbox Database

Hi All,
        I have a client that is running out of space for the exchange mailbox databases.

The environment:-
Server 1: Exchange 2007

Server2: Exchange 2003

Mail is still flowing in Via the 2003 server (not too sure why) to the 2007. All mail is stored in three Mailbox database files located on the 2007.

D:\ Total Size 84Gb available 74Gb - Log files
E:\ Total Size 464Gb available 11Gb - Database

MailboxDB1 - 185Gb
MailboxDB2 - 170Gb
MailboxDB3 - 105Gb

I need to recover some space as you can see only 11Gb is left in place. On Archiving 6Gb of emails from leavers acccounts the Databse did not shrink and drive space continued to drop at the same rate (as if no space had been recovered from the Archiving)

As i need 110% of Hard drive space for a Defrag i can not run that process with the sizes available. There is no availble space within the Server for additional drives so i can not expand local storage.

Possible solutions i have thought of are
1) Move a DB back to the 2003 server & Defrag
         Will this have any impace on the users access email? will clients Outlook need to be remapped to the correct server or will it auto detect?

2)  Create a new DB on the available D drive and begin moving leavers over to this database.

3)  Archiving emails, this is a user education after an office 2003 upgrade on the Terminal Servers. But if the space is not recovered i will still Max out.

Any advice would be well received.

Thanks