Solution:
once a week
Explanation:
Some time user needs to defragment their harddisk when it works slow. because Fragmentation refers to the condition of a disk in which files are divided into pieces scattered around the disk. Fragmentation occurs naturally when you use a disk frequently, creating, deleting, and modifying files. There are lots of sectors on the hard disk and if that sector contains any error value then it can be slow or damages. At some point, the operating system needs to store parts of a file in noncontiguous clusters.