The first backup you / Ghost will do is a FULL backup or image in which it copies EVERYTHING. From there, as long as you tell it do, it will do Incremental or Differetial backups. Difference between the 2 is the Incremental backups only adds any new files and directories to the existing FULL backup. A Differential backup simply records any changes you made to the backed up image. Ghost is also a great way to make a restore CD for your PC. Load the OS, Service Packs, Drivers and all patches, games, programs, etc, as you would use them. Then make a complete image of your hard drive. Then if your system gets hosed by a virus or one of the many other nasty bugs lurking about , you simply pop in your restore CD, and POOF!!! - you're backup and running in only a fraction of the time it would take to do a full install from scratch.