There is another aggravating step that needs to be done on the client side. If you don't know it, save yourself the time and just unjoin the client from the domain, delete the computer account from the domain and give it time to replicate or push replication and then just rejoin.
If it is a critical server or has some odd ball software that this will upset, then search technet for it. You'll need a couple of things installed on the client computer to do it. If it's a server it may already have it.
It really should be a lot easer to do this. I've done this once just to try it. never again unless i have to. Though once you have the stuff installed on the client, it's just a fairly simple command.
