The built-in defragmentation tool provides a streamlined interface to the Windows Disk Defragmenter which will optimize and order the data on your hard disk drive for faster file access.

Windows 9x

windowsdirectory\defrag.exe

Windows NT+

windowssystemdirectory\dfrg.msc

Windows Vista

windowssystemdirectory\dfrgui.exe

Windows XP

windows\system32\dfrg.msc

See Windows documentation for more help on how to utlilize the defragmenter tool.