Même si sur Mac et Linux, il n’y a pas besoin de le faire, il faut faire de la défragmentation sur un disque dur sous Windows.
Il y a différentes programmes qui le font :
Et la suite en anglais
Defraggler lets you defragment your entire hard drive, individual folders or individual files at your option. It is also able to defragment your free space, so that all the unused hard disk space is gathered in one big chunk. The defrag utility also supports RAID drives. The program works on Windows 2000, 2003, XP, Vista and 2008. Both NTFS and FAT file systems are supported.
WinContig allows you to defragment your hard disk, folders and/or individual files. It works on Windows 2000, XP and Vista. You can also use Windows Task Scheduler to create defragmentation schedules. It can either (at your option) defragment a file into the first free area it finds, or look for an area that best fits the file you are defragmenting. If there is no space big enough to fit the defragmented file, it will try to defrag as much of the file as possible.
Ultra Defragmenter is a defrag tool for Windows 2000, XP, Server 2003 and Vista. You can control it either via the graphical user interface (GUI) or the command line. It is released with source code and is distributed under the terms of the GNU General Public License.
JkDefrag is a Windows 2000/2003/XP/Vista disk defrag utility that runs automatically on all your drives when invoked. You can force it to defragment only a particular volume or file if you wish (via the command line), although the default is to defrag everything. You can also invoke it via administrator scripts, run it in the background via Windows Scheduler, and use the Windows Screen Saver version to run whenever the screen saver is invoked.
Auslogics Disk Defrag
Auslogics Disk Defrag works under Windows 2000, XP, 2003 and Vista to defragment your hard disk.
Contig is a command line defragger for Windows NT, 2000 and XP. You invoke it from a Windows command prompt with the name of the file you want defragmented. It’s useful if you don’t want to run the built-in Windows defragmentation tool just to defragment a single file.
PageDefrag defrags your Windows page file, Registry hives, event log files and hibernation files. These are files that the built-in Windows defragger is unable to defragment since they are open for exclusive access when Windows is running. PageDefrag is a boot-time defragmentation utility - it reboots the computer and defragments those files at boot-time, that is, before all the subsystems in Windows start up. The utility only works in Windows NT, 2000 and XP.
SpeeDefrag is a program that restarts your computer and runs only the Windows defrag program. With only the Windows defragmenter running, defragmentation will presumably run faster (provided you don’t count the time it takes to reboot the system). You can also schedule the defrag run, as well as shutdown the computer after defragmentation. The program runs under Windows XP and Vista.
DefragNT (possibly renamed to DefragXP by the time you read it) is a Windows NT, 2000 and XP defrag utility. It supports NTFS partitions only on XP but handles FAT partitions under all three OSes.
Defragmentor Lite CL
Defragmentor Lite CL is a command line tool that allows you to defragment a file or group of files. It works on Windows 2003, XP and 2000.