I read Nitro's article about passwording levels. He says that it's better when you don't put a password on your levels. I find it o.k but how do I remove the password then?
If I just fill in nothing, it still asks for a password!

Impossible. You can't remove a password.

Create a new level and put the stuff from the old level in the new level without a password.

Uh heh, thats sensetive information. Send the level to a person such as me and i will do it for you, however don't ask for the way to do it off anyone please.

EDIT: wait a second am i getting the impression its not your level? If so ask the maker for the password and if they don't wish you to have it tough cookies.