How to convert evaluation copy of Windows Server 2012 r2

 If the server is running an evaluation version of Windows Server 2012 Standard or Windows Server 2012 Datacenter, you can convert it to a retail version as follows: 

1.  If the server is a domain controller, you cannot convert it to a retail version. In this case, install an additional domain controller on a server that runs a retail version and remove AD DS from the domain controller that runs on the evaluation version.
2.  Read the license terms.
3. Open command prompt with administrator permission:

- DISM /online /Get-CurrentEdition

- DISM /online /Set-Edition:ServerStandard /ProductKey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX /AcceptEula

For the evaluation version of Windows Server 2012 Standard, you can also convert to the retail version of Windows Server 2012 Datacenter in one step using this same command and the appropriate product key.