In Windows, search for FOLDER OPTIONS. Be sure that the "Show hidden files.." item is enabled. 
Data files can stay. If this effort fails, use this free utility to delete the program and allow it to scan and delete all VP registry files when it prompts.
Don't know why VP prompts repeatedly for registration, if it initially confirmed that the program is licensed. That should be stated at the top of the VP window.
The fact that these issues cannot be replicated hints at a PC problem. Try another, if one is available. And don't forget to save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. From the HOME tab, that choice is available by clicking the chevron to the right of the Save Project button on the toolbar.