will do this. They can also be a .log file and a .bat file and some .ini files. But other programs cannot have their extension changed and still work. Try changing a .dll file to something else. Or .exe to .com.
I have always wondered about this... We have an application that creates a file with a ".pro" extention. Part of our process is to change the file's extention to "dbf" so it can be read by access. I can also change it to a .txt file and open it with notepad.
What does changing the files extention do, it seems like all it does is tell which program to use to open it?