I just started working with emacs 22.1 and tried to use ediff.
It didn't work. The result was as follows:
Reading file c:/emacs-22.1/bin/myfirstemacsfile ...
Reading file c:/emacs-22.1/bin/myfirstemacsfile~ ...
Computing differences between myfirstemacsfile and
myfirstemacsfile~ ...
apply: Searching for program: no such file or directory, diff
You need a `diff' executable program in your path. Perhaps you just need to
correct your path, so Emacs knows where to find it. You need either a Windows
native `diff' program or a Cygwin `diff' program.