Free Radius used on Linux Flavors and for windows you will have to use "Cygwin" which will be bit difficult .
http://freeradius.org/download.html
Better use Win Radius for Windows as this is easy to implement and configure.Check the following link for install and configuration of Win Radius for Wireless Clients.
https://www.youtube.com/watch?v=wX-5whfP490
Software download link.
http://www.freewarefiles.com/WinRadius-V_program_3929.html