Defragmentation and Scan Disk
Defragmentation.
Disks are divided into sectors (see text). When a file is saved, it is saved in the first sector that is vacant. If the file is too large for that segment, the file manager assigns it to the next vacant sector on the disk. Often these sectors are not contiguous. When such a file is retrieved, the computer must spend extra time finding the sector. Defrag places all the sectors of a files in contiguous sectors. Consult the help section of your computer to decide when and if to defrag the computer. See http://www.webopedia.com/DidYouKnow/Computer_Science/2008/disk_defragmentation.asp for a good discussion of this topic and how to for XP and Vista.
Vista users will find that this utility is set to automatically run once a week, Wednesday at 1AM. If the computer is not on then the utility will run the first time it is turned on. (This is why booting may take so long at that time and other processes slow down.)
ScanDisk (ChkDsk)
Most disks, particularly hard disks, come with, or develop a few bad sectors. It is important to keep files from being written to these sectors to prevent corrupt, or un retrievable data. When the utility ScanDisk finds a bad sector it marks it to prevent data from being written to it. There does not seem to be general agreement on when and how often to use this utility.
Created March 24, 2009