The domain membership is going to be based off the SID of the client install, which will change when you format and reinstall the OS. So, you will need an admin to rejoin the box to the domain (yeah, I know that if a machine account is created in the domain first it's supposed to work without the admin, but that rarely works properly and this account was already active with a previous install and has to be updated with the new OS installation SID) to get you started. After that, you can either logon and restore from the profile backup wizard, or you can logon, then logoff and copy over the old profile directory. The second method creates the proper profile directory with the domain membership, and lets you copy all your old stuff over without having the OS bypass it (if you moved the directory over before your first logon in the domain) and appending "DOMAIN" to the end of the directory name.