Laptop: You could try installing GNU/Linux on it if XP is a no-go.
G3: If it's the school's, not much you can do. Looks like it has a dying monitor. The internet issues are probably just a crappy internet connection at your school, or a misconfigured firewall. I've had good luck with Debian on my G3, but I doubt the school would allow you to do that.
_________________
WAR IS PEACE
FREEDOM IS SLAVERY
IGNORANCE IS STRENGTH