C:\>D:\EX2K13\setup.exe /PrepareAD /OrganizationName:Exchange2013 /IAcceptExchangeServerLicenseTerms
There may be a chance you may get the below error message
Setup encountered a problem while validating the state of Active Directory: Could not find any Domain Controller in domain excharch.com.
To resolve this issue,
Run the Windows PowerShell or the Command Prompt as Run as Administrator and run the same command.