Try kontact. It contains kmail, kalendar, kaddressbook, knotes, ktodo, etc.
It's a full suite that runs on any system that supports KDE (GNU/Linux, OS X, Windows)
I use it on GNU/Linux Fedora 11 though
Screenshots:
www.kolab.org/screensh...ct-windows
Download:
winkde.org/pub/kde/por...installer/
Download Note: kontact is part of the KDEPIM package
P.S.: i'm downloading it now to my Windows7 VM to see what it's worth on Windows