It took me a while to settle on it, but I've finally decided on Mandrake 9. I've tried most of the popular Linux distros, including RedHat, Slackware, Phat Linux, Corel Linux, and everything in between. I don't know why, but I just found Mandrake 9 installed more smoothly and generally ran better. The only trouble I ever had was getting my Geforce4 working, but even that didn't take long.
I'll admit I still use Windows more, but that's mostly because I'm so used to it. I'm gradually easing myself into Linux, and rather than booting back to Windows when I need to do something I'm not sure how to do in Linux, I'll spend a bit of time trying to figure it out instead.