Authenticating Windows Variants (2003, XP and 2000) clients and linux boxes using freeradius

Hello, I am just planning to deploy free radius on a linux box having LDAP, openssl. I have two queries: * Is it possible to authenticate Windows Variants (2003,XP and 2000) clients without using Windows 2003 AD? * And how much I can scale (my requirement might go upto 250 boxes in future) ? Thanks In Advance, Bipin