Quote Originally Posted by Hsu
Essentially what you're doing is removing a layer off of the disc, and evening the surface out so that your reader doesn't skip when it reaches the point of the scratch. That's why you need a toothpaste with a gritty texture, and also why you go from the inside-out rather than going with the grain of the disc.
The Disc Doctor that I have does just that. It works perfectly every time. The only time this has failed to fix a CD for me is if the scratch was severely deep. The picture crash posted looks somewhat similar to the machine I have.

Of course, if the toothpaste thing does work, it is much cheaper.