Isopropyl Alcohol, its available at any electronics shop, like maplins. Best off getting it online, I get mine from Farnell or Buck and Hickman.
The paste is between the processor and heatsink, you remove the keyboard (on most laptops) and the processor is directly underneath, then remove the heatsink and clean the top of the processor and underside of the heatsink and then reapply a little grease.