I accepted the upgrade from P3Dv5.2 to 5.3. In the process I lost my scenery addon files, backups and everything!
Now I have found my most favourite scenery addon (NZNR) but it needs other libraries to be installed for it to work.
One such item is the Vector Land Class Object Libraries. However, this will not install in P3Dv5.3 because it "cannot find the installation path of P3Dv3 in the registry".