Ubuntu and Mac OS X will, similar to UAC prompt you for your password to do certain things. This is not as easily disabled, especially on Ubuntu. UAC is Good and Wrong.
on Vista the password prompt looks different depending on why you are needing to elevate privileges. This struck me as a pretty huge bug, as anyone who managed to spawn a popup window might seem equally credible to the one generated by the OS.
Ubuntu's is exactly the same each time and looks very clearly like part of the OS. And it's not annoying in the least.
