It cleans your pc and improves performance. Another program you can use is defraggler and it defrags your Hard drive http://www.piriform.com/defraggler
Also try and remove old programs that your dont need and such. Hope I helped Take care and good luck.
Yeah there are various softwares available to do so but i think it will not affect much though because the main thing is the processor and the speed fully depend upon the processor...there are various utility softwares for those like Advance System Optimizer and many more...if you want i can give you just pm me