What do u mean disk defragmentation?

Deframenting a disk is the process of moving little pieces of information from scattered places on the disk into a compact sections, so that more information can fit.

Contrived example: Say you have 15K available on your disk:
+++++++++++++++
You create a file that’s 5K
XXXXX++++++++++
You create another file that’s 3K:
XXXXXYYY+++++++
And a third that’s 4K:
XXXXXYYYZZZZ+++
Now you have 3K left. You want to create a file that’s 5K. Obviously you don’t have enough space. So you delete the 3K file:
XXXXX+++ZZZZ+++
But you still don’t have enough space. Your computer can’t find any place for that new 5K file to go. So you defragment your drive:
XXXXXZZZZ++++++
Now you can create your 5K file:
XXXXXZZZZAAAAA+

Think of it as similar to compressing your trash basket. You know you can fit that empty box of rice in the trash, but first you have to press all the garbage down to fill in the individual bits of free space, before the box of rice will fit on top.

This also has the benefit that your computer can access existing data more quickly, because all the data is compacted to one area of the disk, rather than spread out over the whole thing.

In Windows XP, you can find the Disk Defragmentor tool by going to Start -> AllPrograms -> Accessories -> System Tools -> Disk Defragmentor. If you’re using another operating system, try to find the nearest equivalent location.

Hope that helps!

You were doing well up to ”...you delete the 5K file”

XXXXX+++ZZZZ+++

You do have enough space, you have 6K free, its just in two lumps but its still 6K – leaving you with…

XXXXXaaaZZZZaa+

The 5K file gets split across the available blocks. Now imagine your file system doing this over and over again as you delete and add files. (Which happens every time you save an alteration to a word file for example so even when you dont think your doing anything the files can get fragmented).

If you have lots of files in little pices all over the hard drive it takes longer to access them as the hard drive head has to physically move further to alter them.

Defragmenting tries to move all the files about so they are in as few pices as possible. Bear in mind that you need some free space on your disk to do this as it involves copying stuff around so the computer needs a gap to put stuff in while its making space. The other thing to remember is that windows built in defragmentor cant move certain files like the page file and systems files that are being used so even after you run it there will be some fragments left.

Thanks for the clarification/correction.