Installing SQL Server on a Domain Controller

Installing SQL Server on a Domain Controller is not supported by Microsoft.  If you must install SQL Server on a Domain Controller, then you must create a NT AUTHORITY\NETWORK SERVICE account on that computer.  Information on how to do this can be found on the MSDN website: NetworkService Account.

Novell have a good visual guide to setting up a NETWORK_SERVICE account for their software.  This may be a good place for you to receive guidance: Steps to setup NT AUTHORITY\NetworkService as the logon account.