Transfer of Active Directory

I am building a new box(will be running Server 2003). I need to transfer the active directory from the older server to the newer server. The older server is also running Server 2003.

I need to know ASAP. I would like to have detaild instructions that I can also be able to print off and save for a rainy day.

—EDIT—

I aslo need to know what to do when the two servers are on the network. Wouldn’t they clash over the network? If so what would I do.