What does defrag do?

Defrag simply compacts and organizes files and folders on your hard drive.

The problem arises because of the way data is stored on the hard drive.

When you delete a file, all you are doing is removing the index, of where the data is really stored.

When you then save stuff, reference is made to the index, to find out where the free areas are, on the disc. Use is made of all the free areas on the disc.

The free spaces may be smaller than the new file being stored. So the file is broken up and parts of it located all over the physical drive, blotting up the free space.

Over time, your drive is full of fragmented files and the drive has to work harder and longer to find all pieces of file, slowing it down.

'Defrag' locates all pieces of broken files and writes them to a fresh area of the disc, so that they are located in one 'contiguous' physical space. It then clears the disc where they were located. Once enough clear area is provided the whole files are then relocated into the space in such a manner as to keep all relevant files close together and so speed up the access time of the hard drive.