Thank you for this very useful registry tweak.
Update: Well, not so useful. I had a JPEG today from NASA's Cassini site, and I wanted to open it with something other than GIMP. Right-click, Open-with, and the program I wanted to use wasn't there, so I selected "Choose other program" - bam, notepad. So apparently, "choose other program" doesn't mean "choose other program" - it means "set MIME type = unknown". 🙁