Unlocking files on Windows 2003 server

Is there any way to unlock files in Windows 2003 server without rebooting the server?

I am referring to files that are locked by a process, rather than a user. When trying to change the file, users receive an error. The files are usually Word docs or the like; these are not OS system files or anything like that.

For example, when trying to rename, this error is received “Cannot rename : it is being used by another person or program.”

When managing to the server via Computer Management and checking the Open Files, these files do not appear on the list.

I have found several 3rd party utilities that can be used for unlocking files, but I am looking for a native way to do it within Windows.

Any ideas would be appreciated.