In this paper, we present techniques to recover useful information from disk drives that are used to store user data. The main idea is to use a logging mechanism to record the modifications to each disk block, and then employ fast algorithms to reconstruct the contents of a file (or a directory) as it existed sometime in the past. Such a consistent snapshot of a file may be used to determine whether a given file ever existed on disk, to undelete a file that was deleted long ago, or to obtain a timeline of activities on a file. This can also be used to validate that a file with given contents existed at some time in the past or to refute a claim that a file existed in a time interval. Information gathered using these consistent snapshots can be used as valuable digital evidence.