You need to change what program Windows associates with that type of extension. It sounds like the file type you are trying to open is associated with notepad.exe. You'll need to change that to the program that can read that type of file.
everything from windows media player to video games or ventrilo. everything i open opens with notepad, wen i reboot all my exes open in notepad, not system ones but user ones that i have start up on startup