When trying to promote a Server 2012 to your existing Server 2003 domain or Server 2008 to be a domain controller then you may come across this issue after installing the Active Directory Services role.
Exception: Access is denied.
Adprep could not retrieve data from the server server01.contoso.local through Windows Management Instrumentation (WMI).
Check the log file ADPrep.log in the C:\Windows\debug\adprep\logs\2013011734560-test directory for possible cause of failure.
This fix for this is quite simple. I am used to naming a server then simply running DCpromo into the domain it then joins the domain and becomes a domain controller, this was standard practice in Server 2003 and Server 2008.
In Server 2012 to get around this issue join the server to the domain first then reboot before promoting it to be a domain controller.
Additionally this may be a WMI or firewall error. Check out this Microsoft article.