[Quelty]

Ok, in control panel select "Folder Options", then in the dialogue box that comes up select the "File Types" tab, wait for the list to populate, scroll down and click on MAT and you will see a "Change" button...click it and a dialogue box will appear with a list of programs...select Notepad...if notepad is not in the list select "Browse" and navigate to notepad.exe (in C:\Windows).

Hope this helps

Cheers

Quelty