Automatic USB Backup comes in four editions: Standard, Professional, Realtime and Backup & Synchronize. Backup & Synchronize is the full edition with all features enabled, while Standard, Professional and Realtime are the limited-functionality editions. It's compatible with Windows Vista, XP, 2000 and 2008/2003/2000 Server as well as Windows 7.
Click the Compare Products you can find a comparison of the features available in each edition.