It is good idea to use the Defrag and Disk Cleanup utilities that are built right in to the operating system.  Defragmenting reorganizes files that have been moved around over time.  If large data files are created and deleted, this will create gaps on the hard drive.  Later on when other files are created, they will be stored in whatever space is available.  Defragmenting a hard drive simply groups data into a contiguous form. 

 

You might want to run Disk Cleanup to get rid of any files you no longer use.  This will also compress data and possibly free up some hard drive space.

 

To use Disk Defrag, click Start > Programs > Accessories > System Tools > Disk Defragmenter.  Once that window is up, right-click on the hard drive and select Defragment.

 

Disk Cleanup is located in the same path as Disk Defragmenter.  This program will automatically detect any potential files that could be removed.

 

If large files are being used ( >10MB) on a constant basis, defragmenting a drive should be done at least once every couple of weeks; otherwise, at least monthly would be recommended.