Try this one in notepad.

Type any sentence in this sequence of letters:
4 3 3 5 –(e.g: musa mnk the great or Bill fed the goat)

then save it n close the notepad,
See what happens when you open it again.

You can now see all the text in it is converted into a bunch of squares. Actullay I dont know whats behind this, may be a bug in windows!