Michael is correct, and to clarify further, the scratch drive is simply the hard drive you are importing (capturing) ur material onto. Ideally this shouldn’t be ur Macintosh HD because it’s a less safe way to do things and is marginally slower as well hence why an external HD is so useful, assuming it doesn’t corrupt. DON’T buy a cheap one or it WILL die, go for a reputable brand like western dgital or lacie 🙂