Came across an undeletable file today at work on a network drive.

The only thing that stood out was it had an @ ( AT symbol ) in the name.
It wasn't hidden or system, just plain ascii, but gave either:
"Could not find this item" or "You need permission to perform this action".
The normal tricks of using Attrib, 8DOT3 name, Robocopy, all failed.

Narrowed it down to any file, in a subfolder, over a network share, with:
@GMT-0000.00.00-00.00.00 ( zeroes can be any digit )
anywhere in the file name becomes protected from rename or deletion.

Seems it was intended to guard Volume Shadow Copy data files, but anyone is allowed to create or rename a file with the above in the name.

The solution was to log on to the server and delete directly from the local drive.