Fragmentation happens over time as Windows writes files, deletes files, and writes new files to your drive. Files end up in fragmented segments all over the drive. Then, when Windows reads a fragmented file, the drive must work hard to move its read-write head all over the drive to retrieve the file. Also, if a file becomes corrupted, data-recovery utilities are less likely to be able to find all the pieces to the file if the file is fragmented rather than written on the drive in one location. For these reasons, you should defragment your hard drive every week as part of a good maintenance plan. Defragmenting rearranges files on the drive into as few segments as possible. Identify defragmentation problems.