Give Unlocker a go:

http://ccollomb.free.fr/unlocker/

It has many other flavors:

Cannot delete file: Access is denied
There has been a sharing violation.
The source or destination file may be in use.
The file is in use by another program or user.
Make sure the disk is not full or write-protected and that the file is not currently in use
It will unlock any process that might be accessing or stopping you from deleting the file.