The whoami.exe command comes with Windows Vista and later, but for those on XP you can download it as part of the XP Support Tools here.
0
Chad Rexin
On
If you have administrative rights in Active Directory, you can run Active Directory Users and Computers and look at the Account tab of the User Properties window and see it with it being a combination of the User logon name and the domain suffix (first one listed).
This command should work.
The whoami.exe command comes with Windows Vista and later, but for those on XP you can download it as part of the XP Support Tools here.