For revision control we've been using CVS under Windows for about 6 months and it has been working quite well. The server portion is running under an NT based server (Win2K). The client software installations allow access to the repository from a DOS shell, from extensions in Windows Explorer, and from its own visual interface (wincvs).

Someone else on our team set this up & my impression is that it is somewhat involved to get setup, but it seems to be very full featured and it's free (open source GNU license).

For more details, see www.cvs.org, www.cvsnt.org, & www.wincvs.org.