You don't seem to understand what I said. Firefox (or any other program for that matter) should be able to install itself when run by an under-privileged user.

You don't seem to understand what I said. Firefox (or any other program for that matter) should be able to install itself when run by an under-privileged user. SHOULD. If it CANT, then its installer is designed incorrectly and its installation mechanics are wrong. Consider a simple case when I am on a shared computer as a restricted user. In an Internet cafe or similar. I should be able to install, run and use Firefox. There's basically no technical reason why it will not be able to run under a restricted set of privileges. It has no drivers to install, it doesn't bind to privileges range of ports, it doesn't need to install a service. It should quietly go into C:\Users\dude\Program Files and make itself comfortable there. Microsoft has a set of guidelines, in part covering where what should go. Some of these guidelines are simply retarded, they have always been. Their existence is not an excuse for not questioning them. If a developer insists on following them, it just doesn't speak much of a developer.