How do you copy or back up Windows Server 2003?

We are running out of space on one of our servers and would like to reconfigure it from a Raid 1E (it’s an IBM) to a Raid 5. I don’t think this can be done without destroying the data on the 3 hard drives in the array and I want to back up or make an exact copy of our current configuration that includes domain controller settings, AD settings and accounts, and all other files.