Hmm. IIRC "Chess Titans", which comes with Windows 7, is very easy to beat on the lowest level.
In addition there is a good little free chess program for Android phones called "Chess for Android", by Aart Bik, that is very easy on the lowest levels, and even offers a level where the computer plays by randomly choosing any legal move. Chess for Android also offers optional move hints (once a piece is selected, target squares it can reach are shown in green) and can be used as a portable chess board for two human players in its "free play/analysis" mode.
