Sorry Tom I don't think I explained myself properly.
The reg code is fine (you are absolutely correct that the code is not machine specific, it is tied to the username) as demonstrated by the fact that when I use the install file on another computer and use the same reg code everything is hunky dorey.
I am convinced that something is screwed up on my laptop that is messing with the registration. To the extent that I am seriously thinking of a fresh OS install (it hasn't had one for about 4 years!)
I am fairly sure that the reg code for pro is different from standard as that is the only difference between the instellations - but of course I could be wrong, it has been known
I have requested a new code just in case but as I said the code I already have does work so I don't really expect that another working code will change my situation much.
I don't mean to sound ungrateful, I really do appreciate your input.