First, click to Start->Run, type sysprep and press OK.
This will open sysprep folder which is located in c:\Windows\System32. Open sysprep application.
This will open System Preparation Tool 3.14 window. As a System Cleanup Action select Enter System Out-of-Box Experience (OOBE). Important: select Generalize if you want to change SID, it’s not selected by default. As Shutdown Options select Reboot.
It will take some time for sysprep to finish, so grab a cup of coffee and wait.
After rebooting you’ll have to enter some data, for example, Country or region, Time and currency and Keyboard input.
Also, you’ll have to accept EULA. And that’s it. After booting, in Server Manager you’ll see that everything is changed, if you had some settings set now they’re changed.
Now you can again use PsGetSid to check that your OS has new SID.