A.B.
A little googling found Toddler Keys 0.97. It's free and you can find it at this web site:
http://www.download.com/Toddler-Keys/3000-2132_4-10305344...
I have not personally used it but it looks a lot like the mac program you were talking about. I do believe I'm going to go download it because my 14 month old has always insisted on hitting the keys. She has used more random short-cuts then I never knew exisited.
Good luck!
*update*
I downloaded the program and my little one loves it! You get to pick your own sounds and pictures so I picked a whole bunch of pictures of her. When she hits the keys, turns the mouse wheel, or clicks the mouse a picture pops up of her. When she moves the mouse around it draws with a little mulitcolored line. She thinks it is just so great! She also can't turn the computer off or open the driver doors with this program. I'd recommend it!