System Optimization is necessary if your computer is getting slow. Over time your computer will become cluttered with temporary files and old deleted files that cause drastic decreases in speed. There is an easy fix for this problem but may require some sacrifice.
Some programs are worse than others in causing this trash to build up on your computer. One of the worst is AOL. They install tons of information on your computer that you will never need. Then it plagues you as it slows down internet connection, boot times, and file searching.
Some other programs that have this affect are costly security suites such as Norton or McAfee. Anti-virus is a necessity in todays spyware infested world wide web, but in this case, free is always better.