Not sure why the thread above is locked, but I did want to point out that it can be played full-screen (or at least full browser page) by going directly to the host site. URL is as follows:
http://www.hybridarcade.com/swf/flashtennis.swfThe play control can be difficult to get a handle on and is for simplicity's sake not very varied, but still entertaining for all that.
I've had the most trouble with, not surprisingly, Navratilova, Graf, Evert, and Davenport, but own all of them now. I've won Kournikova's first title for her, broke Kimiko Date's SF duck at the majors, and completed Seles's career Slam finally. :P