Changing back to Windows Shell Commor

Hi,

I recently opened a 'savegame' file using notepad. I now find out that i cannot get it to play properly. I realize that i have to change it back to what it was originally, however i am unable to do this. I need to change it back to Windows Shell Commor/Common.

I have downloaded a program called 'Unassociate File Types' however i am not very clever and i don't really know what to get rid of.

Thanks for any help i receive,
Maisie