I    selected "always use this file" when opening an attachment, but find that some files will not SAVE in NOTEPAD - which Ichose for speed of opening.  How do i RELEASE this binding to Notepad?If a copy of the email remains  on Thunderbird, point to the attachment and save as another name to your desktop.

Point to the desktop icon, right click and choose open with.  Choose Word when the EXTENTION is .doc.  Choose MS Office Power Point viewer when the extention is ppt or pps.

If you only have the ORIGINAL saved icon, repeat above steps and choose another program.  The program you choose depends on the extention. The old choice of always use notepad will be repaced by your new choice.

If a new default is not established, you may always use the steps To open the file.Important security rules:
1. Never open any attachment directly from the email program. Always save, first.
2. Scan every saved attachment with your AV program, before opening. Even, if it appears to be from someone, you know.