No, I use Linux.
I'm on Ubuntu right now. My computer came with Windows Vista Home Premium, but my hardware wasn't strong enough to support Vista, so I wound up installing Ubuntu with Wubi on the live disc.
In fact, my mom got this cheapo old computer from a friend, and once she gets it running I'm going to look into installing Damn Small Linux on it. It's currently running a pirated Windows XP and is slow as hell.