Over time, files on your computer get fragmented. Fragmented files are those that are stored in non-contiguous sectors of the hard drive. Since a hard drive loads a file or program faster when it resides in contiguous sectors (I.e. there is less jumping around to get the file or program) your PC will respond faster when its files are defragmented.
Windows comes with its own defragmenter (Start / All Programs / Accessories / System Tools / Disk Defragmenter). However, I personally think that it is slow and works poorly.
A better option is a free program called Auslogics Disk Defrag (http://www.auslogics.com/en/software/disk-defrag/). It works very well and provides two levels of defragmentation – simple and optimized. The former works very quickly while the latter takes longer to run while it helps to keep files from fragmenting in the future.
