Hidden encrypted volumes can cause problems in digital investigations since they provide criminal suspects with a range of opportunities for deceptive anti-forensics and a countermeasure to legislation written to force suspects to reveal decryption keys. This paper describes how hidden encrypted volumes can be detected, and their size estimated. The paper shows how multiple copies of an encrypted container can be obtained from a single disk image of Windows Vista and Windows 7 systems using the Volume Shadow Copy feature, and how the changes between shadow copies can be visualised to detect hidden volumes. The visualisation assists in the presentation of this information to a court, and exposes patterns of change which allows the size and file system of the hidden volume to be determined.