type in search engine vob to avi and this will come up with a number of software to do the conversion!
download.com is a good place to start. vob is a DVD file format and so a dvd ripper can easily change this to the required format needed! I usually work with my own video materials which are usually in the correct format for use so i am at a disadvantage to say which work best as it relates to the various brands available, the star rating are usually reliable though so you can be guided!!