Here's a few programs and games off the top of my head. They are all free (and/or open source). Some of it may be too advanced for his age but maybe you can show him how to do some things and he'll figure out a use for them.

General:
- GCompris (many activities, graphics are a bit crappy though).


Graphics:
- Paint.Net (freeware paint program)
- Inkscape (FOSS clone of Illustrator)
- Leocad (3D editor for Lego-style constructions, can be used with lego instructions)

Audio:
- Audacity (better alternative than the default sound recorder)
- I was also thinking some oldschool Mod Tracker but I can't remember any that has a piano style interface.

Games
- Neverball (3D ball game, similar to monkey ball)
- Supertux (Mario clone with a penguin)
- Lincity (simcity clone, available for windows, get the basic version which is top-down 2D).
- Tux Racer
- Frozen Bubble

Now you may think why bother with these clones when you can use the originals? Well they are somewhat different and in some cases simpler.

Retro - Apple II:
These are the ones I played when I was 7 - probably still fun today.
- Lode Runner
- Pacman
- Gold Rush (not the Sierra adventure game)
- Galaxian II
- Space Eggs
- Oregon Trail
- Some text adventure games by Scott Adams [adventureland, lost dutchman gold, etc]
- Sneakers
- Clone wars
- Dino Eggs
- Wavy Navy (there's a remake available made in Python)
- Eliza



[download a life]