Does Linux hide extensions too? Not with the file manage I'm using, Nautilus.
Yes, most Windows users don't know what they're doing, my dad thought that by renaming an odt to a doc it would work with Word.
One thing that would help is, when renaming files Windows would only automatically highlight the text before the extension which would make it less likely for them to change the extension; I know Linux does this.
The security problem can also be solved by only allowing executable permissions to files in the Windows and Program Files directories but goodness knows whether this is possible for Windows and if it is, it'll probably break all kinds of things.
Regarding notepad; is word wrap enabled? I don't know about Vista but with XP the line numbers aren't displayed when word wrap is enabled.