KDE is an excellent one to start with, but you may notice some differences that may become annoying: In order to open things, you SINGLE click it - like Internet style! Gnome is also a fantastic desktop system, which does feel a little more like Windows. To top them all, though, you could try ICEWM2 (or whatever it's called). KDE's start bar is a K, Gnome's start bar is a foot, and ICEWM2's start bar is 'Start', just like Windows.
I personally prefer KDE because it's just that little bit different you can't just relapse back into Windows User mode :-)