If the data is "important" to your friend, then I would definitely reccomend R-Studio. There is a limited demo version on their site, which will up-front show you what it will be able to recover after you pay the US$50 fee.
After you recover the friend's data, then it's time to play, and you can see how much you can get with Knoppix. I found this book valuable.

SiKing.