Duplicate SID when cloning Win 2008 R2 VMs

If you’re reading this, there is a strong chance that you are learning via a home lab setup. I faced an issue while I working on my home lab. I created a 2008 R2 source VM to be cloned  as multiple VM later. After lot of steps, I ended up with two 2008 R2 machines, one already as a Domain Controller (DC). While attempting to promote the other 2008 R2 machine as DC, I got an error that said, this machine is already a domain controller.

Being a novice, I spent lot of time figuring out that because I cloned the second machine from the first, they have the exact same Windows Security Identifier (SID).

To avoid this, follow the below steps to Generalize the SID of your source VM Image before doing the clone.


  • Go to C:\Windows\System32\sysprep
  • Run sysprep.exe
  • Choose Options as below
  • Hit OK and the VM will make changes ans shutdown.
  • You can now clone from this shutdown VM without having duplicate SID problems later