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.