Windows Disk Defragmenter is a handy tool that may help you gain some extra performance from your PC. When Vista writes to your hard drive the bits of information that make up a file can be spread all over the disk (this is called fragmentation). The "defrag" tool will try to join up all of the parts that makes up files so that they are in the same location, decreasing the time it takes to find all of the parts.
To load Windows Defrag, run from the run box (Press WINDOWS KEY + R to load this). In this window you can choose to "Defragment Now" if you wish to perform this operation now, or alternatively you can schedule a time for your PC to defrag automatically (ideally when you are not using your PC):
If you click the button to defrag immediately, you will be informed that this is in progress but there is no graphical indicator like in previous versions of degrag.