Finding real time backup freeware is not that easy. I found AutoVer, and it seems pretty powerful and straightforward. Here is a small explanation from their website: (for more info, browse to their site, URL see below)
AutoVer is a configurable automatic or real time backup and personal versioning system. It can be used as a simple real time backup or as a more complex, but transparent version control system (like a realtime incremental backup). The beauty of this system is that once you set it up (which is extremely simple) it does everything. No remembering to backup or to check in or check out files. Every time you save a file it is copied to your backup folder, drive or FTP server. You can include and exclude certain files and browse the backups with the Backup Explorer.
Great for backing up (or one way synchronising) your work or home documents to flash memory or saving every change you make to your source code or image files.
You can find this freeware at http://beanland.net.au/AutoVer/.