I think it might be because slow double-clickers (or other people) may inadvertently rename the file extensions out of existence.
This guy probably isn’t too happy with Vista right now. The Windows Activation security feature of Vista made his system unusable after he swapped a video card and updated some drivers. Nice that your computer can be made unusable with no warning and no recourse other than jumping through Microsoft’s notoriously bad customer-service hoops. I won’t be “updating” my wife’s XP machine to Vista. No way.
I had to disable Automatic Updates, a feature I had once found useful, after Microsoft slammed Genuine Advantage down my throat. The “Advantage”, apparently, was that I got to be treated like a criminal even though I’d paid them an outrageous fee for their piece-of-shit software. Hooray!