Vista Ultimate help! Local user lost administrative rights

Hello. A co-worker brought in his laptop from home to our company. About a month ago i was able to map the network drives to his computer. recently he had only partial access to the files and folders and he was trying to sync them? I was then able to add him using my login but now his local account believes it to be the domain login, even though the login is “local/User” where as our domain login is “Falmouth/user”. He has access to his original desktop, icons, documents. but no administrative rights. Also the default admin account was never enabled. Any insight would be greatly appreciated.