Exchange 2010–How to Move a DB

1. Run a full MB job to commit and purge log files into the DB
2. Open the EMC, then nav to org config, mailbox, on the db management tab select the DB, right click and select dismount database

3. Once the database shows the mounted status as dismounted, right click and select move database path.. In the file paths, simply change the drive letter, or change the entire folder destination per your needs, then click the move button and let the EMC take care of the rest.

4. After completion, if successful you will see it completed successfully

5. Restart the Microsoft exchange search indexer service

6. Right click on the database file under the org config, mailbox, on the db management tab, and select mount

Technet related topics that will also help you are below.
http://technet.microsoft.com/en-us/library/bb123903.aspx
http://technet.microsoft.com/en-us/library/dd351168.aspx
http://technet.microsoft.com/en-us/library/bb123587.aspx