Managing SQL Server Express databases
If you need to copy, move, or delete a SQL Server Express database, you must first detach the database from the server. Do not detach a database currently in use.
To determine whether a database is in use, do any of the following:
Verify that the date included in the file name has passed.
Check whether a database with a higher number exists for the current date.
Enter the following lines at the command prompt, to list as SQL Server Express databases that currently have open connections:
OSQL -S computer_name\MSFW -E sp_who2 go