Marty, this guy (sorry if i got the gender incorrect) is a Linux Newbie. Knoppix is a fine distro, and i use their live DVD, but it can be a bit difficult to install for a newbie. Sure you want to steer him or her in this direction?
AFAIK, Ubuntu/KUbuntu/XUbuntu (they're all the same distro, they just use different windowing environments) are much simpler to install.
PCLinuxOS is easy. In my opinion, even easier than any Ubuntu I've tried, although I haven't tried the new verions of Ubuntu Mint. I would go for PCLinuxOS 2007 as that distro sets up everything. It's the ONE linux that got me away from Windows. There is also PCLInuxOS MiniMe that is a minimal install where you select what additional programs to add from Synaptic.
Of course, I bought a new computer with Vista two weeks ago, and I'm still playing around with it, haven't dual booted yet.