I decrypted the DVD using the decrypter that comes with the computer
This statement makes no sense to me. Are you actually using the program called DVDDecrypter? It is outdated as a decryption program and doesn't always remove all the structural protection schemes that have been introduced since development stopped on the program.
Try decrypting and ripping the dvd to the hard drive with DVDFab HD Decrypter. It is free to use and will continue to function even after the trial for the main section of DVDFab expires.
Convert to avi using AutoGK, or FairUse Wizard, or Xvid4PSP.