Okay I have found an old email re the purchase. I'm terribly sorry for all the confusion.
It says I have paid for V17 but for some reason I have only ever had V16 on my system.
I'm now wondering whether I initially tried V17 in its early infancy and it gave me some grief so I reverted to V16 which was stable for me.
That email was dated 10th Feb 2012.
After all that how will my using V16 effect to use of Screen Shot?
Regards Cazzesman