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16 free disk defragmenters to boost performance

When a file is saved to the hard disk drive we assume that it is stored in one continuous block on the disk surface and that each file is a complete, whole and separate object. This is true quite a lot of the time, but it doesn't always happen and not all the files on the disk drive are stored as a continuous block from start to finish.

Many files that are on the disk are split into many small fragments with a bit of file stored here, a bit there and the rest somewhere else. Fragments of a file can be scattered all over the disk surface and they aren't always located near to each other.

You don't notice that files are split up into small fragments and stored all over the disk surface because Windows keeps track of where all the fragments are and when you want the file it goes and gets each part in the right order and reassembles the original file.

You may be wondering why and how files become split like this, and it doesn't seem a logical thing to do. To see how files can become split into two or more fragments when they are saved, imagine that you saved three files called A, B and C. This is how they are organised on the disk surface:


If you then delete file B there will be a gap between file A and C where B used to be stored, like this:


If you then you save file D Windows might start saving it in the first bit of empty space it finds, but if there isn't sufficient room for it, the rest is stored in the next bit of free space:


You can see that part of file D is stored in the space left by B and the rest is stored after file C. File D is now in two fragments. The advantage of splitting files when they are saved and filling in the gaps between existing files is that it makes very efficient use of the space on the disk because every little bit gets used. If a file could only be saved if there was a large enough space to store it as a complete block without any breaks you could end up with a situation where there was lots of free space on a disk, but you couldn't save a file because there wasn't a free block big enough. You would be able to save a small file like a text document, but a large video clip might not be able to be saved.

The disadvantage of filling in all the little spaces when a file is saved is that when a file is read back from the disk the operating system has to go and find all the parts. Accessing a fragmented file takes longer than one that is saved as a single block because Windows has to jump around fetching the fragments. Disk performance suffers and the computer gradually slows down over time.

This is one of the reasons new computers are fast, but then they slow down as they become older. It's the disk contents that become disorganised and fragmented. Fortunately, a disk defragmenter is able to reorganises the disk contents and it pieces together the fragments of files and resaves them as complete blocks. It improves the performance of the disk drive and in turn this speeds up the computer.

Iobit SmartDefrag

Of course, Windows has a disk defragmenter, but it is far from perfect and some people would say that it is barely adequate. Third party tools do a much better job, so let's take a look at some disk defragmenters that can boost reassemble fragmented files and boost performance. These are all free.

Free disk defragmenters

Puran Defrag

There are free and commercial versions of this defragmenter and the free one is for home use. It offers to install Babylon 9 during the setup, but it can be deselected because it's not needed. It is one of the few free utilities to include boot-time defragmentation and this enables system files that are in use to be defragged. It has some nice features, such as auto-defragmentation with lots of useful options and an option to stop if a laptop is running on the battery.


When you unzip the file you'll find several executables. Run JkDefrag.exe and the disk defragmenter starts working straight away. There are no menus or a pretty interface, although a graphical file map is displayed. There's a command line versions and perhaps best of all, a screen saver version. It's useful to defrag when the PC is idle. It can't defragment files that are in use though.


This is a competent disk defragmenter and it has a nice interface that is easy to use. It's frequently updated with new features and some are not obvious, so scour the website and forums for tips. A useful feature is the ability to list files that are fragmented and to sort them into order according to the number of fragments. You can select individual files and defragment them instead of doing the whole disk. It can't defragment files that are in use though.

Smart Defrag

This is an excellent disk defragmenter that has features not found in some of the other free tools and this gives it an advantage. It can analyse disks and show a fragmentation report, it offers three different types of defragmentation methods, and it runs in the background and defragments the disk whenever the PC is idle. It can't defragment files that are in use, but it's one of the best freebies and is recommended.

Disk Defrag

This is one of the simplest disk defragmenters and it only offers basic defragmentation. There are few options and while it performs the task quickly, you will probably prefer the extra features that you get in rivals like Smart Defrag. Only one defragmentation method is available and it just joins up fragments into whole files again. It can't defragment files that are in use.


This lacks an installer and a graphical interface - you have to manually install and uninstall it, and type in commands at the command prompt to get it to run. This means that it is only suitable for expert users that know what they are doing. Certain files, like the page file, can't be defragged, but this is common with freebies.


This is a simple command line disk defragmenter and it isn't suitable for novices. If you don't mind entering commands and command line switches then give it a try.

Diskeeper Lite

Diskeeper is one of the best commercial disk defragmenters and XP's Disk Defragmenter is based on an old version of the software. This free Lite version is no longer available from the Diskeeper website, but it can be found elsewhere. It doesn't work at all in Vista. It's past its use-by-date.

Ultimate Defrag Freeware Edition

This free edition of Ultimate Defrag is quite good and there are a range if useful defragmentation options, such as consolidating free space, most recently accessed files and so on. Unusually, it has a disk shaped file map. The options make this one of the better freebies and it is well worth trying. No boot time defragging for files in use though.

Power Defragmenter

Go to the downloads section and get Power Defragmenter if you want a graphical front end to the Contig disk defragmenter. It's a very basic interface for Contig, but it does make it useable by novices. There are better defragmenters available though.

Disk Defrag

You don't get a disk defragmenter and instead this is a front end to Microsoft's Disk Defragmenter. It adds options such as the ability to shut down when it is complete, or to restart. It aims to run Disk Defragmenter under optimal conditions so that it does a better job.


A major problem with all the free disk defragmenters here are that they can't defrag files that are in use, such as the page file, registry files and so on. This utility does just that. Use one of the other tools to defrag the disk and then run this utility to defrag the files the others can't touch. It's an essential add-on.


Like Disk Defrag, this aims to optimise the built in Disk Defragmenter. It restarts Windows and runs Disk Defragmenter first before anything else is loaded. It can therefore defrag files that are normally in use and it should work faster too.


With more configuration options than the usual freeware disk defragmenter, this is definitely one to consider. You can choose from two defrag methods, set the priority, hide the window, shot down afterwards, check the disk for errors, and more. Well worth trying.

Ultra Defrag

There are a couple of defragmentation options and you can either defrag or compact files. A right-click context menu enables you to defrag individual files too. With only 335k to download, it's a tiny program, but it works quickly. It crashed Vista, but there's a lot of rubbish on the test PC that could upset it.


This is a very basic command line utility and it seems to be similar to Contig. If you are OK with the Dos-like command prompt then give it a go, but if you need a graphical user interface then skip it.