Without knowing your DBMS, my first suggestion is that you measure the space used after you complete the system copy (but before you do the client copy)...
After you complete (and validate) the client copy,
delete the source client
unload / export the database using your DBMS tools,
redefine / recreate the filesystems underlying the database,
and import the database.
If I was in a trolling mood, I would have suggested going into the SQL Server Management Studio and shrinking the database 