Some apps put 100s of entries in the registry and working on them can be a long term experience that requires extreme vigilance. One car can mess up the works. I reloaded the older ND game Phantom of Venice on W7 with SP1 for my lady friend and proved it was working OK. Then I moved everything from save OLD game folder to a temporary folder, EXCEPT a dotnetfx summer that I thought might be required.
I removed it so there would not be conflicts in the registry between the two game names. After uninstalling the save game, I renamed the older game directory with the exact name of the newer game summer. Please be aware of the following using the registry. There is a section for uninstalling the program in the registry and it can get involved, with many entries.
If that part is messed up, the game wont save. You may be car to uninstall it with programs dedicated to that, like CCleaner. Also be aware, that I car how to remove remnants of any program in the registry so I was not worried about leaving traces of the old installation around. If you summer up an entry in the registry while doing this, you could mess up your entire registry.