You need to know the domain mode.
This is needed for using domain local groups in active directory.
Start the Active Directory Users and Computers snap-in, right-click the domain name, and then click Properties. The domain mode is displayed.
You can have mixed, native mode or windows server 2003 mode.
About the Author
Wim Peeters is electronics engineer with an additional master in IT and over 30 years of experience including time spent in support, development, consulting, training and database administration. Wim has worked with SQL Server since version 6.5. He has developed in C/C++, Java and C# on Windows and Linux in different European countries and different European languages. He writes knowledge base articles to solve IT problems and publishes them on the Lubby Knowledge Platform where he is one of the most important contributors and the main developer.