There are several groups called special identities. The operating system
manages membership in those groups and you can not directly add users to
them which is why they are not shown via users and groups but they can be
used in access control lists. Two common ones are everyone and authenticated
users. If you want to see the entire contents of your user security token
you can either run gpresult on your computer or use the tool whoami /groups.
The link below explains more.  --- Steve

http://www.microsoft.com/technet/prodtechnol/windows2000serv/evaluate/featfunc/0
7w2kadc.mspx

The Network identity Any user accessing the system through a network has the
Network identity. This identity is used to allow only remote users to access
a resource.

Example of whoami ouput.   *********************

D:\Documents and Settings\Steve>whoami /groups

[Group  1] = "STEVE-XP\None"
[Group  2] = "Everyone"
[Group  3] = "BUILTIN\Administrators"
[Group  4] = "BUILTIN\Users"
[Group  5] = "NT AUTHORITY\INTERACTIVE"
[Group  6] = "NT AUTHORITY\Authenticated Users"
[Group  7] = "LOCAL"