Sorry, I tried to explain that.
The change for V6 was to register the Rhino Installer Engine as an application. In V4 and V5, we didn’t do that so there was no application registered with Windows. This made it a bit more confusing. The easiest way to “fix” this was to “repair” the Rhino installation.
As of V6, you will have a registered application associated to RHI files so it’s a little easier.
Basically, we’re crappy developers and don’t know what we’re doing.