Giving a Netbook to a 4yr old. What to load on it?

nostrodecus writes: I have a nephew who is very young, but who has the techie gene — he found the Gruffalo on youtube before anyone knew he could spell. Now he's almost 4, and I was thinking of giving him my netbook (Acer running XP), which i hardly use any more. So of course I will be deleting all the porn, but what should I load up on it? Are there tools/apps that I can load up on it to protect it and him from things he shouldn't see until college? Also, what apps or games could I load on it that a 4 year old will get some use out of?