I tested again and it's for sure: the Compare function is unable to create a new temporary snapshot of the actual registry status (to compare afterwards with the previous (partial) snapshot created (without any problem) by the user (= me).
Why? I don't know. Is that temporary snapshot created in the default temporary folder of jv16 PowerTools? I guess so, because a new subdirectory is made in my temporary system folder.
So, why is Compare not able to write the new temporary snapshot to that subdirectory?
However, as far as I know, there's nothing wrong with my temporary system folder, unless it's not in the default Windows temporary system folder, like e.g. \Windows\Temp, but on another drive, e.g. D:\XX\TMP. But that shouldn't be a problem, shouldn't it?
I have placed a debug log here in this thread. I wonder what the programmer has seen in it...