To assignNTFS permission to files or folders on a windows xp computer in a workgroup , you need to turn off simple file sharing and enable local users to authenticate as themselves. You can do this in one of two ways:
Simple file sharing is disabled by default in windows 7:
Log on as a user with administrative privileges:
open the control paneland click network and file sharing centre.
From the left side click the change advanced sharing setting link
Then select Turn on file and printer sharing and turn off password protected sharing and click save changes.