Check for duplicate Security Identifiers (SID) on your domain

Active Directory, Windows 7, Windows Server 2003, Windows Server 2008 R2, Windows XP,

Mark Russinovich makes a strong case for duplicate SID myths that most of us Windows admins have subscribed to–however it never hurts to know how many duplicates you may have. Here is how you check it on your domain.

Open a command prompt and type 

 ntdsutil

 and press ENTER.

Now type 

 security account management

and press ENTER.

Now type 

 connect to server DNSNameOfSAMDatabaseServer

 and press ENTER.

Now type 

 check duplicate sid

and then press ENTER.

If you have duplicates it will be listed.