Microsoft Drive Optimizer  Microsoft Drive Optimizer (formerly Disk Defragmenter) is a utility in Microsoft Windows designed to increase data access speed by rearranging files stored on a disk to occupy contiguous storage locations, a technique called defragmentation. Defragmenting a disk minimizes head travel, which reduces the time it takes to read files from and write files to the disk. As a result of the decreased read and write times, Microsoft Drive Optimizer decreases system startup times for systems starting from magnetic storage devices such as a hard drive. However, defragmentation cannot be run on storage devices such as solid state drives, USB drives or SD cards that use flash memory to increase speeds, as these drives do not use a head. Defragmentation may decrease lifespan for certain technologies, e.g. solid state drives. Microsoft Drive Optimizer was first officially shipped with Windows XP. From Windows 8, the program was renamed to Microsoft Drive Optimizer, with some references changed to say "Defragment and Optimize Drives" or simply "Optimize Drives". As early as the end of 1982, the IBM PC DOS operating system that shipped with early IBM Personal Computers included a Disk Volume Organization Optimizer to defragment the 5¼-inch floppy disks that those machines used. At this time, Microsoft's MS-DOS did not defragment hard disks. Several third party software developers marketed defragmenters to fill this gap. MS-DOS 6.0 introduced Microsoft Defrag. Windows NT, however, did not offer a Defrag utility, and Symantec was suggested by others as a possible alternative for the utility. Initial releases of Windows NT lacked a defragmentation tool. Versions through Windows NT 3.51 did not have an application programming interface for moving data clusters on hard disks. Executive Software, later renamed Diskeeper Corporation, released Diskeeper defragmentation software for Windows NT 3.51, which shipped with a customized version of the NT kernel and file system drivers that could move clusters. Microsoft included file system control (FSCTL) commands to move clusters in the Windows NT 4.0 kernel, which worked for both NTFS and FAT partitions. However, Windows NT 4.0 did not provide a graphical or command-line user interface. Disk Defragmenter also shipped as part of Windows 95, Windows 98 and Windows Me. It could be scheduled using a Maintenance Wizard and supported command line switches. This version had the limitation that if the contents of the drive changed during defragmentation, it rescanned the drive and restarted the process from where it left off.