After certain time, because of the removing and adding of files, fragments are developed in a disk. The used blocks and the unused blocks are spread everywhere in a disk. When the disk is fragmented and if a new file is created, then the block so this file will be spread everywhere in the disk and hence the performance is reduced. To solve this problem, the used blocks should be kept contiguous in one region and the unused blocks should be kept in another region. This process is known as disk defragmentation. Disk defragmentation does not move all the files especially files like paging files and hibernation files. These files are known as unmovable files.
Disk can be defragmented for a particular drive in Windows XP. If you wish to defragment all the drives then you have to do it one by one. Here are the steps to defragment a drive in Windows XP:
1) Go to: Start –> All Programs –> Accessories –> System Tools –> Disk Defragmenter.
2) Select a drive.
3) Click on Defragment.