If you are on XP or 2000:
open ControlPanel->AdministrativeTools->ComputerManagement. Then under
"Shared Folders" click "Open files" subtree. It should show which
process is the locker.

If only VS is running, it's VS that is accessing the file, are you sure
there is no application started from within VS that has the file open?

Willy.

Check all of the services running on ur PC

You can use SysInternals' freeware ProcessExplorer (
http://www.sysinternals.com/Utilities/ProcessExplorer.html ) to search
for open handles and other useful stuff.

This often happens with me after viewing a file or folder's properties
using Explorer on XP Professional. Sometimes for no apparent reason,
Explorer appears to lose track of the open file descriptor, and I must
log off completely (or kill explorer.exe) to delete the file or folder
in question.

As with what other people have said, the SysInternals utilities prove
extremely valuable when figuring out problems such as this.

David.