Haha... What immediately comes to mind for me is a "game" called "Fin Fin". I had it when I was a kid and loved the heck out of it.
The premise was that was an alien planet occupied by this half-dolphin half-bird creature that would fly around to six fixed-view locations and live its life. Interaction was entirely limited to:
1. Offering a fruit to Fin Fin in one of the locations.
2. Beating a drum in one of the locations.
3. Talking into the microphone at Fin Fin, which never had any effect I could detect except startling him if you yelled.
What made it awesome was that the planet had its own ecosystem with a bunch of bizarre animals and plants which you could catch glimpses of. It also worked in real time based on your system clock and calendar: The time of day would change with reality, seasons would pass and seasonal plants would grow and die. There were a few special events that only happened once per (real) year. There was also weather and stuff, it was so cool. [/nostalgia]
I basically played it as a wildlife photography thing, trying to catch screenshots of all the animals, some of which I only encountered once in a couple years of playing.
That said, it was a commercial product and even if you can find it, I don't know if it's even possible to make it work on XP, to be honest.