I think it is when data is being written to a disk, if there is not enough space, then it will set a flag and continue to write i the next available memory block. It may be caused when a file is amended. When the computer is defragging, I think that it is re-spacing the data so it is more uniform and less sporadic.

You mean what causes disc fragmentation. For speed programs dump data in the nearest available spot on your hard drive. When the program is run it always has to locate and retrieve that data and that takes time (though only milliseconds). When you 'defrag' your 'puter puts all that remote data for all your programs where it is more readily accessible (usually with the program it belongs with). It's sorta like 'straightening up' yo...

Defragmentation is the process of locating the noncontiguous fragments of data into which a computer file may be divided as it is stored on a hard disk, and rearranging the fragments and restoring them into fewer fragments or into the whole file. Defragmentation reduces data access time and allows storage to be used more efficiently. Some operating systems automatically defragment storage periodically; others require that the user occasionally use a special utility for this purpose. Windows 98 comes with a built-in defragmenter as a "system tool" that the user can run. Windows NT did not come with a defragmenter because its file system, NTFS, was designed to minimize fragmentation; however, NT users often find one necessary and several vendors provide defragmenters. Windows 2000 comes with a "light" version of the Diskeeper defragmenter; some users (especially corporate users) use Diskeeper or some other full-function defragmentation program to manage storage efficiency and performance. Windows XP comes with a utility called "Disk Defragmenter." "Defrag" is a short form of the verb to defragment and sometimes the name of the utility used for defragementing, which is also called a defragmenter. as to your question can it be avoided no, if you use the computer, its going to happen. I once tryed to explain to to a much older lady, and finally came down to saying this: your at the library all is in order from A-Z but bunch of kids hae taken the books and put them back out of order, along with files in some of the books being misplaced so this robot comes in and puts everthing back in its place. she was happy and understood then. I told her she didn't do any thing wrong to cause it, it just happens with time. If your running XP here are instructions for doing it. DISK DEFRAGMENTER XP 1. START 2.ACCESSORIESS 3. SYSTEM TOOLS 4. DISK DEFRAGMENTER 5. CLICK THE BUTTON THAT SAYS ANALYZE 6. THE PROGRAM WILL THEN ANALYZE TO SEE IF COMPUTER NEEDS TO BE DEFRAGGED, A BOX WILL COME UP SAYS YES OR NO TELLING WHAT IT NEEDS. JUST CLICK IT. 7. IF YES, THEN JUST WATCH IT DO ITS THING, IT NEEDS no HELP FROM YOU, DEPENDING ON HOW BAD COMPUTER IS OUT OF ORDER, COULD BE 10 MINS OR 2 TO 3 IT WILL STOP ON ITS OWN AND THEN YOU CAN SEE RESULTS AND CLOSE PROGRAM. ** Even though it says defrag is not needed do it any way!!

Even there is not any virus in your computer, it still cannot work fast as before, why? If you are an experienced computer user, it does not seem difficult for you, because you can defragment disks when the computer is becoming slow. It is really a good method to optimize computer performance. Well in this article, I will tell you the main causes of disk fragments in a hope that it can help you prevent the disk fragments in advance. The major cause should be blamed for the virtual memory programs. If there is not enough physical memory to run the application, the operating system can produce temporary swap files in the hard disks. Such file virtualizes the hard disk space as memory so its program can do massive read-write operations to the disk and create fragments. At the same time, during operating the files such as moving or deleting, Windows system may apply virtual memory to manage applications synchronically which may lead to the frequent read-write operations of every program to hard disks. This is another main resource of disk fragments. What is more, if any sector is removed and then the system reads a new and smaller file into it, there may be some empty space beside this file. And if the system continues to write more files into this disk, the space between those two files can not put any new one any more. That is to say, the file has to be divided into several parts in order to put in the disk. See, file fragments are produces again. If you are a movie fan and like to download from Internet, you have to pay close attention to the disk fragment problem. Once you are doing other operations during the downloading process, the film files are forced to separate into certain fragments and restore in the disk. So, downloading is one of the main causes of disk fragments. Besides, if file space is not large enough to support the frequent deleting and adding files operations, it can bring about a huge number of disk fragments as well. Such problem can go from bad to worse on the condition that you do that hourly. Generally speaking, sometimes you may not be aware that when browsing websites or playing games, it can produce a mass of temporary files in the computer. Or when downloading video in your hard disks, it is easy to produce a lot of disk fragments. If you find computer performance is not so good as before, I suggest you to defragment disk firstly. When performing defragmentation, please close down screen saver and do not do anything else in the computer such as listening music or playing game but just let defragmenting program run by itself. By doing this, you can not only speed up defragmenting speed but also prevent the program from starting again and again. If you want to avoid hard disk fregmentation, please go to learn more details here: http://advanceddefrag.com/blog/disk-fragmentation-%E2%80%93-how-to-avoid-disk-fragmentation-2/