The Disk Defragmenter is a very useful tool for keeping your pc in good working order. You need to ensure that you defragment at least once a month if using regularly, although this depends on how you are using the system. The system becomes defragmented over time if alot of copy or move operations are occuring, so downloading alot of data especially from p2p applications will cause the disk to become defragmented and would start to slow the system down considerably and may even lead to the system crashing, bad hard disk sectors or even a complete hard disk malfunction. You must therefore ensure that the disk defragmenter is running. In Vista the need to run the disk defragmenter manually has been put aside as now it runs as standard as a scheduled task. You can still initiate a defragmentation however by opening the Disk Defragmenter application from control panel or elsewhere.
There are many differences between the disk defragmenter of Vista to the previous versions such as XP. One main difference is that you now need administrator access to open the application, other differences include the fact that all disks are now defragmented at the same time with no immediate option to select a particular disk or even see which disks are more or less defragmented than the other. You also do not see the defragmentation process in a graphical manner aswell as the analyse disks process from previous versions. The new version seems a much simpler application and more stable than the previous version. It is hard to tell from the gui application though some nescessary details, however you can go into the command prompt and type defrag which would enable you to gather more information and more advanced options.
Choosing to modify the schedule brings up 3 options, you can choose the frequency at which the process will run, you can choose a day of the week and you can choose a time of the day. Click Ok when you have made your changes or cancel to keep the current settings.
If you want more control over the defragmentation process, run command prompt, but right click on the shortcut and choose to run as administrator beforehand. Then at the command prompt type defrag you will get many options similar to previous versions of the disk defragmenter in Windows XP but through the command console.