Hi Gary,
First off Happy Birthday! I've had better luck deleting stubborn registry keys in Safe Mode. To do this push the F8 key before the Microsoft Windows splash screen (with the blue or green bars going from left to right). You have to be quick though with that F8 key as you only have a few seconds. Choose Safe Mode from the menu list given and try to delete those registry keys again. Reboot normally back into 'normal' mode and try to install again. Hope this helps!
P.S. Just waiting a few days on a focuser for that OTA I bought off you
Troy