C$ share local access

I administer an NT4 domain with 60 PCs, two BDCs and a Unix server. A workmate imaged a workstation system to a larger hard disk using Power Quest Drive Image. The trouble is that after the user logs on the OS asks for username and password for the administrative share C$. It also asks for username and password when one of his desktop shortcuts is run, namely Act 2000. There is no problem when logging on as Administrator. It seems to be a permissions problem. Or is it something to do with the user profile. Is there a fix for it to avoid reloading the OS and apps?