Your hard drive is a bit like a big filing cabinet which can get very disorganized over a period of time if it never gets sorted out --- and just as it takes ages to find the file you need in a mixed up filing cabinet; the same is true of your computer accessing the data on the hard drive. This extra activity can put a lot of pressure on your system and mayslow it down and/or cause crashes.

You need to defrag your hard drive regularly (anything from every week if you are using your pc for audio/video down to once a year if you're not too worried about performance) ... probably every few months is a good rule of thumb, but it all really depends on your usage.

If you are installing and uninstalling programs regularly it is very important to keep your drive defragged. In fact if you are installing a new application, especially a large or important application like Photoshop, MS office or AutoCAD then it's good to do a defrag first (This gives the application a big chunk of free space in all the one place so it is not broken up into lots of little pieces on the drive.)

How to defragment ?

The process takes a while to complete - usually not advisable to wait around unless you have a very small drive and a very fast pc. Of course if you have a large drive and a slow pc it might be a good idea to set it up to work overnight as you may be getting into the multiple hours area.

Defragment all your drives except the floppy(A), dvd and cd/cdrw drives.

N.B. As the drive is defragmenting you may notice a message saying that the drive contents have changed and the process is restarting. If this problem persists then it may be better to start again, this time putting the machine into safe mode first.

safe mode ...