It shouldn't matter either way - the Rhino RHI installer should handle the entire installation process, and it's rare issues like this arise, so not something I have a lot of experience with. It appears in your case the installer is not functioning correctly - so perhaps deleting those folders first might help. You could also delete the 3.2.0.66 folder, since you are trying to install a later version of the plugin.Should I delete the 2.24.2.51 and 3.0.20.65 folders before I re-install?
Paul