Performing the following steps:
- Exit Windows Media Player.
2. Click Start, click Run, type %LOCALAPPDATA%\Microsoft\Media Player, and then click OK.
3. Select all the files in the folder, and then click Delete on the File menu.
Note: You do not have to delete the folders that are in this folder.
4. Restart Windows Media Player.
Note: Windows Media Player automatically rebuilds the database.
If this does not resolve the problem, clear the Windows Media Player database cache files. To do this, follow these steps:
1. Exit Windows Media Player.
2. Click Start, click Run, type %LOCALAPPDATA%\Microsoft, and then click OK.
3. Select the Media Player folder, and then click Delete on the File menu.
4. Restart Windows Media Player.
Were you sharing the files?
See the command line for disabling Network sharing service
https://msdn.microsoft.com/en-us/library/windows/desktop/dd562624(v=vs.85).aspx
Have you tried booting into Safe Mode and deleting the file?