The best product you can use is from "NOVUS," You know, them people that fix them rock chips in your Windshield!!! They have a Plastic Polish & Scratch remover compound that they make in three stages, (1)Fine (2)Medium (3)Heavy, they cost about $8.95 a bottle, you most likely would never need #3 so just grab a bottle of #1 & #2, This stuff works.. I never heard of a sharpie maker working and dont see how it can. The plastic maybe scratched on your disc but that does not mean the data area is scratch. the data is burned into the back side of the label and if you use a marker on the side of the disk that the lazor reads then I would think it could not read through the mark that the pen made, same go's for a disc that has scratchs on the label face, hold it up to a light, if you can see light through the disc then that data is gone. Remember, the disc itself is just a piece of clear plastic that is protecting the data burned into the back side of the label.