sentences:  Software packages for Windows are also sometimes distributed as disk images including ISO images.While Windows versions prior to Windows 7 do not natively support mounting disk images to the files system, several software options are available to do this; see Comparison of disc image software.Virtual hard disks are often used in on-the-fly disk encryption ("OTFE") software such as FreeOTFE and TrueCrypt, where an encrypted "image" of a disk is stored on the computer.