Also, if you still got the 'older' version of the white Macbook (the one with the matte white plastic inside, NOT the plastic-unibody one), cleaning the plastic is quite easy with a product called Magic Eraser. I used this to clean my old iMac G4 and tried it out on my flatmate's old Macbook as well- worked perfectly and his white Macbook from 2007 now looks like new