File sharing is one of the most potent functions in a network. FTP, Netbios and other means are widely used and they work great. The only problem is that they are not secure enough. I have used this OpenSSH server on windows for a long time for file sharing and today when i am installing this on a different pc, i thought i would share it here as well.
Complete instructions at http://pigtail.net/LRP/printsrv/cygwin-sshd.html
Basically, you install Cygwin and choose the ssh option in it. While you are there, check the other options as well. You may very well fall in love with this.