How to know whether a server is Domain Controller or not

You can find in three ways
1) By log on dialogue box
If it is a Domain Controller at Domain Names you won’t get “this
computer” option.
If you get “this computer” option in a server Operating System that must
be a Member Server.
2) By My computer Properties
On Network Identification tab, the Properties button will be disabled.
3) By typing DCPROMO
If it is already a Domain Controller you will uninstallation wizard for
Active Directory.
If it is not a Domain Controller you will get installation wizard for Active
Directory.
4. You should see the share of netlog and sysvol … just type netshare at the
cmd prompt
5. You should be able o see the ntds setting in the winnt directory
6. You should see the ntds folder in regedit ..