I agree with Arti - there is just no way that CS3 just happens to come fully loaded on a new PC legitimally... it's either just a 30 day demo or is an illegal copy or he paid significantly more money for the software already configured on the PC (ala Dell's software options).

If it is the full version, where did he buy the computer from?

If it is the full version... I'd just start using it. CS3 is the best paint program on the market so if you have it for free - just start small and learn it. Takes a few months to get comfortable but will pay dividends for you once you fully get it.