ArcServe 6.61 Backing up Registry

I am currently using ArcserveIT 6.61 for WinNT to backup my files on a remote server on the same domain. Backup files get backed up with no problem but when trying to backup the registry it gives me an error message: Unable to connect to network drive (Drive=\\nj-ts1\ADMIN$, ES=ACCESS DENIED) Any help would be appreciated.