Fire, you JUST missed out.

Overlord discontinued his Overlord.exe download on his site about two years ago.

For prevent people edit them. What would you use it for anyway?
If you just are going to "look and learn", contact the athour and ask him/her for the password. They proably wont mind you have it.

Passwording levels is dumb. There is only 1 kind of level that you need to password and that is a test level that has passwords in it to continue from other levels.

Meaning my new test level: Aerial Precision, is the only level I have ever made that is passworded.