If you mean physically - it can't be done. They are sealed in a clean room at the factory. Opening the hard disk assembly outside of a clean room will wreck it.
If you mean clear out files that are no longer needed it depends on your operating system. If you are using Windows then go to Accessories/System Tools/ disk cleanup. When you have done this use the defragmenter tool that you will find there.
t, March 2007
