Whether you're working with the built-in hard drive on your Mac or using an external hard drive to store your files, it can improve the performance of your system if you regularly defragment your hard drive.
In the course of normal use of your Mac, the computer is constantly writing various files, deleting others, and fitting them in to various leftover spots on the hard drive. Like a cluttered room, the hard drive can end up becoming fragmented , where part of a file is on one spot on the hard drive and another part of the same file is stored on a different spot.
This isn't because you've done anything wrong, it's simply the way that hard drives store data. But because of the demands that digital video places on the hard drive, this fragmentation can have a significant impact. Defragmenting basically takes the various bits of each file from various spots on the hard drive and reassembles them into contiguous, nonfragmented files. That means the computer can read the file without having to jump around the hard drive.
To defragment and optimize your hard drive, you must purchase a tool such as SpeedDisk, which is part of Norton Utilities. This suite contains a number of useful tools for maintaining your system (www. symantec .com).