Abstract: A method for performing a write operation to a hard drive or other memory space is provided. The hard drive is represented as at least two files. The first file is a parent drive and includes some content of the hard drive. Writes made to the hard drive are recorded in a second file, known as a differencing drive. Because no changes are made to the content of the parent drive, the content of the hard drive may be rolled back to the content of the parent drive by discarding the differencing drive.

Abstract: A mechanism is provided for making information about the virtual disk image file and/or its associated virtual image configuration file more readily available to a user. The virtual disk image file format is expanded to include fields in which information about the data in the file can be stored. Extensible information on file content, compatible HW configurations, compatible host OSes, timeout status, DRM status, patch state, and network topology, tag data for indexing, configuration files, saved state files, operation history data, and the like is stored in a location within a virtual disk image file that can be read without executing the virtual machine. This information can then be used to search the contents of the virtual disk image, to enforce usage policies, to provide extensibility for vendors, and the like.