One of the steps that the connect to computer wizard does is *OPTIONALLY* add the domain user account that you migrate data for to the *LOCAL* administrators group. This is, as I said, optional and can be easily skipped or gone unnoticed.
Simply log into the machine with a domain admin account and then, using the user manager control panel, find the user you want to grant admin privileges to and make them a member local administrators group.
HTH,
-Cliff