My 2nd DC is Win 2008 standard so I had to lower the functional level of my DC1 to 2008 Standard. After doing this, I still cannot join the 2nd DC to the domain.
The error I get is: The functional level of the domain or forst is incompatible with this operating system."
"The version of the OS installed is incompatible with the current domain functional level. You must upgrade to a new version of the OS before this server can become a DC in this domain".
"This error can occur if you have no been granted necessary permissions to read the data in the directory. For more info, please see 936241 in MS Knowledge Base."