The hacker may have set the file up so it is considered part of the operating system. Even Administrators are not allowed to delete files that are in use by the system (which I suspect may be the problem). Try booting to safe mode (to stop loading of alot of system files) and attempt to take ownership of the file and delete it. If you can't take ownership of the file, you may need to take ownership higher up in the path (folder itself) and have that percolate down to the folders and sub folders). If you are still denied deleting for system reasons in safe mode, you may have to boot to the recovery console from the CD to stop loading of all system files on the hard drive.