The easy way to add a new file type that can be seen in explorer or MyDocuments is to open a window and go to the "tools" link on the upper explorer bar. You then go to folder options at the bottom of the drop down menu and onto the third tab on the new screen that opens. You simply type the 3 digit extension of the the new file there and click the add button. For details on creating a new value in the system registry go to http://www.hermit.cc/teach/ho/win/howinnmn.htm