Windows NNTP Server Software

If you can live with timed backups rather than per save version control, Windows Server 2003 and later have a feature called volume shadowcopy. You allocate space (or a separate disk) and a schedule which will snapshot the filesystem and retain as much as it can based on the space you have allocated. Plenty of tutorials out there on how to do this.

Here you go: http://www.windowsnetworking.com/articles_tutorials/windows-server-2003-volume-shadow-copy-service.html

Your clients must be XP or later to use this feature.