Windows Vista SP1 has a new option for defragmenting drives that is very nice, you can now choose to have any of your disks defraged automatically so that they are kept optimal efficiency. To set up your drives, or just some of them, to defrag automatically, start by launching the Disk Defragmenter utility by typing dfrgui in the Start menu Run or Search box.

Once it runs, you'll see that there is a checkbox to run this on a scheduled basis. Check this box to get automatic defragmenting. Also, make sure the job is scheduled to run at a time when your computer is on but you are not using it. If the time or frequency needs to be adjusted, select the "Modify Schedule..." button.

There is a new button called "Select Volumes...". Click it. This will then list all the drives on your system. Select the ones you want to automatically defrag.

Once you are done, select the "OK" button and you will be set to have your drives automatically defragmented.