NFS/NIS Recommendations for Windows?

Fembot asks: "The Samba team are doing a great job, but I can't help but feel that making Unix machines serve Windows-based protocols is the wrong approach. Back in the days of Windows95 it shipped with an NFS client on the CD which could be installed optionaly. Are there open source (or even just free as in beer) NFS clients for Windows 2000/XP, and is it possible to authenticate users on Windows desktops via NIS?"