Scrap Winows and install Linux. I can recommend two different distros: SUSE and UBUNTU. Stay away from junk like RedHat and TurboLinux. SUSE is more polished and refined, more of a corporate issue type of product. UBUNTU is more for the hobbiest, that’s what I have been running.
I was tired of rebuilding my Windows computer every time I let my kids use it, so now I dual-boot between Windows (for adults) and Linux (for the kiddies). Seems like all the virus-infected stuff and nasty spyware is added to sites that kids like to visit (aim buddy icon sites are some of the worst, any sites with cheats for video games are bad also).
Both distros come with FireFox and Gaim. You may have to do a lil work to add Win32 Codecs and MP3 playback (licensing issues) and, heaven forbid, you might learn something new.