File and folder locks

I have an NT4 server which will not allow me to delete some folders. This is what I have done to date:
1. Reboot owners machine to make sure it has released all locks.
2. Take ownership of the effected folder and remove all access except Administrators.
To delete the folder I have to reboot the server which is done as little as possible.
The folder is not listed as IN USE nor does it appear that any programs are accessing it, so I have 2 questions.
1. Do you know of any way to list which users or applications have placed a lock on the folder in question?
2. Is there an application which will unlock and delete the affected folder.

Thanks for any help.