This happens to me at least once a week. Somehow my default file associations get screwed up by something, which becomes a major inconvenience. In Windows XP it was very easy to modify File Associations by clicking View and Folder Options. In Windows Vista there isn't even a menu, or even a File Types tab... the option doesn't even appear if you right-click on the file. How do I change my File Associations now?
Read on at OCModShop.