Mechanisms for generating an incremental backup of a set of data blocks while excluding certain files that are less desired to be backed up. Examples of such files include temporary Internet files and the recycle bin. This allows the size of the incremental backup to be reduced significantly since such undesired files are often changed between backups. The incremental backup is constructed by first calculating which data blocks should be included in the incremental backup. The calculation is a function of at least the identity of which if any of the data blocks in a prior snapshot have been or would have been altered as a result of potential file alterations in the prior snapshot, and/or which if any of the data blocks in the subsequent snapshot have been or would have been altered as a result of potential file alterations in the subsequent snapshot.