Thanks for the link to the instructions just a couple of questions though - can you run the second server whilst the dc is on? I've got a wsus server set up on an old workstation with server 2003 on so could I use that and have both servers running together? (sorry for beginner question)

If the main DC goes down does the second just take over?

Or if I had a second server ready on a spare disk in a workstation like steveg, can the server name, ip address, and domain name be the same as the original?