?unknown acct. with permissions

I’ve just used Somarsoft’s Dumpsec to list dir and file permissions for an NTFS volume on my NT4SP6a PDC. One directory lists an account named ?unknown with RX perms on dir. and file. This acct. doesn’t show up in the User Mgr. anywhere. Could this be a system or service acct. of some kind that was perhaps deleted by the admin previous to me? Any answers or ideas to investigate would be appreciated.