I have a 2.5-year-old Dell (high-end) from before I switched; it runs 98, XP, and Fedora Core 3.
Mostly, my little sister uses it to play Toontown (Disney's MMORPG), which only works well on Windows 98, since I don't feel right disabling the Windows XP firewall.
I use it maybe for three hours a week, as opposed to far more than that on Macs.