Installing DNS on a 2003 DC

Hi, I did some searching in the Knowledge base, before proceeding with my question.  I seem to have a unique situation.  I have a DC on a subnet that handles our lab PCs on a private network.  The DC is NOT running DNS Server services.  In fact, it is not installed.  I am not sure what the previous server admin was thinking, but this server in question is a DC without DNS.  I thought all DC's required DNS, but some how this DC is working, well most of the time.  Every once in a while I get some weird DNS issues with the lab PC's, which I believe relates back to this DC not having DNS.  Now there are several other DC's that all are running AD-Integrated DNS that are on the public network.  So, I am trying to figure out what would be the point of creating a DC on a private network without AD-integrated DNS on it?

So, my question for the gurus here, how do you install DNS on a current 2003 DC and make the DNS AD-Integrated?

Thanks for your time.