@Giles Jones

Vista doesn't only use the filename for privilege escallation. It will alos ask you when it NEEDS to. The Setup.exe thing is a feature to save you going partway through an install before doing it.

"Vista does, but the access controls are so annoying people turn them off"

It's is more annoying on my Mac since it asks me for a password everytime, whereas on Vista it is just a boolean.

Macs are good, but don't be so blinkered to their flaws.