On one hand you have users who can crash a system.
You haven’t been doing your job if they can do that in normal use. But even if they’re being stupid you should not let them crash it. The monkey test on the keyboard (or buttons) is a popular QA test. The meaner QA people will literally unplug your database or application server in the middle of something. But the meaner QA means less chance of a user being able to screw it up. You do have to protect them from themselves to some extent.
On the start button, good UI principles can erase a lot of user complaints, but at some point you just can’t overcome a user’s stupidity. I’ve seen someone printing over and over and over and complaining the printer’s not working. He had the Microsoft XPS writer set as his default printer. You can’t really do anything about that but try to educate them.
Except on a Mac you see a picture of the printer you’re printing to, so he may have figured out a similiar situation on a Mac by himself.