I have copied the file
favicon.ico from one website folder to another in Windows 2008.
Now I can't delete this file, nor can I change its owner in the security tab even as an administrator.
How can I regain access?
I've found the Sysinternals Handle to be a handy (and free) tool for these purposes.
However, handle.exe works only with local handles, and it doesn't tell who's got the file open. This VBS script finds out who has the file open and it can check files on a remote server:
Sounds like the file has an open handle preventing any modifications of it. Have you tried running Process Explorer or some other utility to search for open file handles and see what process has it locked?