Occasionally I loan out my DVD's and get them back scratched resulting in skips and errors. Sometimes CloneDVD2 will fix minor errors but when that fails I usually try DVD Decrypter which does a better job. Until recently if both of those options fail I just buy or copy another DVD and count it as a loss. But I just found a good, small free program called ISO Puzzle-14 that fixes most errors (caused by scratches anyway). Here is the link: http://www.geocities.com/marsoupilamis/ Be sure to download the dll. at the bottom of the page and put it in the extracted files folder for ISO Puzzle-14 or it won't work. Enjoy, Live well.
@corax57 Another good program is DVDFab Decrypter like DVD Decrypter it does all that and much more except iso's. http://www.dvdfab.com/free.htm