As your particular problem is related to the registry, you should seek the Microsoft data bas, but you might be able to short cut it by contacting Fred Langa direct, as he specializes in writing Registry intence software,contact him at mailto:fred@langa.com , or go to the "Langa List" , just type it in the way I spelled it, in your browser , it should get you the hit. Microsoft can better identify which keys are relevent to you problem, as it wasn't a pristine setup, and now is a user specifictype, print out the fixes suggested by MS or Fred Langa, and go slowly , as the registry allows no errors, if you mess up, you will have to reinstall completely. If you want I will find the MS main Data base access for you , but you should have documentation on what URL to access it with.
Good luck, sorry I am so vague, it's just I haven't experianced your particular problem, Yet.
There are logical steps to all MS setups, and you will have to lay out the steps you have to use, then get the correct documentation to show you how, for each step, because some so-called fixes sacrifices another area to make it work, leaving you in worse shape, this will have to be approached an item at a time.
Good luck , I'm sure you will get it done.
P.S. Check the configuration of one of the other machines, use your ALT+PRINTSCREEN to snapshot it for referance, and paste in a document of graphic application, as that command is a copy of the document you have open as a picture, the latter will allow you to compare the setups to see where they differ, letting you see what is assigned to which.