While using your computer, you have no doubt installed and deleted many files. As new data is written to the hard drive, the spaces left by deleted programs are filled first, even if they are not large enough to contain the entire string of data. This can lead to a phenomenon known as fragmentation, which can adversely affect the performance of your computer.
Fragmentation is when files are stored on the hard drive in several locations that are not directly next to one another.
Installing and deleting programs on your hard drive leads to fragmentation. This occurs because, instead of writing each file to its own continuous sector, your computer stores bits and pieces of data as new space becomes available. As more and more programs get added and deleted, the hard drive becomes more and more fragmented.
Effects On System Performance
When the computer has to access several areas of the hard drive to read one file, access time is greatly decreased. Your computer will seem to run slower while it hunts for data.
Using the Defragmentation Tool
Windows has a special utility that analyzes your hard drive for fragmented files and defragments them when possible/necessary. Access the Disk Defragmenter by opening My Computer. Right click on the C drive, and select "Properties."
How Long Defragmentation Takes
Depending on how fragmented your hard drive is, disk defragmentation can take some time. In cases of severe fragmentation, it might take up to several hours. While your computer will still be functional during this time, it is recommended you allow defragmentation to run undisturbed.
How Often You Should Defragment
In most cases, running the disk defragmentation utility once every 3 months is sufficient. However, if you install and delete files on a regular basis, you may choose to run the defragmentation tool more often.