thats the problem, OS is already installed and system uses those reg key(s) which are locked with XP/serv2003 you could open registry hive and add things, then insert it back to install cd directory and shove it back to ISO dunno if Vista/7 can do the same, try google basicaly your goal is to already package modified registry hive with changes, instead applying changes after/or during install I see, well I have searched and searched and have not found anything useful yet. I'll guess I have to search even deeper . What about converting the reg file to cab (if it's possible)? Maybe it can get around the lock?