I would suggest either Xandros 3.0 OCE or Yoper 2.1 for the beginner. Xandros has the easiest user interface I've seen as well as the most seamless windows networking.
Yoper is almost as easy and really screams. Yoper is configured to take advantage of the i686 architecture and has custom compiled packages for nearly everything. It's one of the fastes distro's out there.
both of them use KDE as a default WM, but it's quite simple to swich to gnome if that's what you prefer or even a more lightweight one such as xfce- well at least in Yoper, I've never tried in Xandros, but with how the OS works, it would seem to be a bad idea in that case.
The great thing about both of them is that they are debian based, giving the user the power of apt to install packages without having to worry about dependencies.
Mandrake is ok for the beginner (though I can't stand it personally), with the redhat package system, but if you want to install beyond the basic system you'll be pulling your hair out on rpmsearch for hours trying to meet the dependencies of each program.