Backup size not the same

I'm using Acronis B&R 10 update 3 with Windows 2003 and XP.

My issue performing a backup of teh C:\ drive is: Using the Advanced View, the General section I leave as default, then select What to Backup- C drive 60GB, Where to Backup I select a shared drive on the same server, the Archive, Backup Options, and Convert to VM are left as default, I don't select any compression or any other settings for this test. The backup completes sucessfully, however, the 60Gb HDD is only about 11GB, is there something I missed?? Th.anks