Change NotePad's Default File Type

I think I remember years ago seeing a tip on how to change the default file type that NotePad opens. I'm not talking about what editor opens when I double click on a particular file but rather the default type that is displayed from NotePad's File|Open menu item. Does anyone know how to do it?

Open notepad in a hex editor and move to offset 0x7b4

You will then see 3 null delimeted pieces of text :
txt

Change the three letters to anything you want, and then also at 0x7c0 and that does the trick.
So now my notepad opens *.aah files by default :)

If I can find an hex editor I'll give it a try, but as I remember it it was something simpler.

This is what I use :
http://www.tu-darmstadt.de/~rkibria/frhed156.zip

Small and easy to use.

If you give me the file type I can send you a modified .exe

Thanks. I'll try to do it myself.