[Sociable]

May pay to back track a little and change your folder view settings so you can see the extensions of all files.

Having done that next step will be to confirm the file you are trying to open has the txt extension and not an EXE which is the way it is being dected right now.

Then right click a known good txt file and check it is set to open with notepad and confirm this is the "official" version of notepad.exe in the main Windows directory by using the "Browse" link. (The true Notepad.exe is located in the main Windows root directory btw)

The above check will at least make sure "normal" txt files are assocaited with notepad correctly and all that will be left then is to check the contents of the specific txt file giving the problem.

My guess is that the file in the attachment is not a valid txt file but possibly a renamed exe file or some form of archive file.

Hope that helps