Glad to hear that it's sorted. I'd be curious, though, as to how the Registry key went 'missing'?
Yes, format/fresh install is the 'easy way out' and yes, it should be seen as a 'last resort'.
Sometimes, however, it is also the
best course of action. People should refrain from trotting out that piece of advice with careless abandon, but also should not hesitate to give it when warranted.
If that missing regisrey key, for example, has occurrred after some rather ill-advised tinkering on the system, one problem fixed might well be followed by several more soon cropping up. If there is underlying system corruption which a refresh install doesn't adequately correct, then a fresh install is certainly a preferred oiption over fiddling around tracvking down numerous problems one by one.
Horses for courses