How can i most thoroughly clean hardrive for performance?

Hi, about a year ago I bought an Asus laptop, model G60J (read about it here http://www.asus.com/Notebooks/Gaming_Powerhouse/G60J/) I bought this computer to have a powerful gaming laptop, which it has delievered on. Lately I notice it freezing up, and processing much slower. I have moderate computer skills but need to know how to more thoroughly clean my computer out, and any other tips to help boost performance. I already run ccleaner on it very often. Any tips would be enormously appreciated!!