Howdy Kombrig,

No you haven't made any fatal mistakes - but when you uninstalled MNC, Windows no longer had a program that was "associated" with the .not files, and that's why you don't have the cute little icons by those files right now.

All you need to do is run Notation Composer, and use the "Setup/Associate..." command. Check which files you want to have associated with Composer (.not, and probably .mid and .kar as well), then click "ok". Now, when you look at your file lists, you should see the little icons restored, and when you double click those files, Composer will open them.

ttfn,
Sherry