Does anyone know how to join 5-6 vob files together to make 1 larger vob file?

I decrypted a dvd with Dvd Decryptor and it created 5 different vob files. I want to join them together so I can see the movie without any interruptions. Does anyone know of a free software which can join several vob files together into one larger vob file? You would be very helpful. Or does anyone know how to change the settings of Dvd Decryptor so that it produces only one vob file? If so, could you please answer this question.