Thanks for the replies.
I can open the files in Microsoft Word, and also in notepad in a different computer.
Should I just delete notepad.exe and copy and paste new file from the installation disk? What if I cannot find the installation disk?
I am also curious how this happened. Is it some type of virus? I can usually find info to fix problems and to see cause just by typing something in google, but this time I could find any site out there talking about this specific problem.