Is he just converting dvd movies or does he have multiple vod's that he wants merged into one avi?
If he is wanting to converting dvd into avi I have been using a free program called bitripper and is a one click application. This program though will only rip and convert from a dvd but not VOB as far as I know.
bitRipper is FREE DVD to AVI software that allows you to back-up your DVD's as AVI files on the hard drive. It can be used for one-click ripping as good as for advanced modes. You are free to choose whether to use default configuration values or to set them manually. There are all necessary settings available:
* Video and audio codecs configuration
* Video resolution and aspect ratio
* Sound track language and sound value normalization
* Variety of actions to be performed after the copying process is completed
* Includes 3rd party decryption module for CSS protected DVDs
bitRipper does not require gigabytes of space to copy all DVD content to the hard drive before converting to AVI. It converts video on-the-fly, copying data and writing it to AVI file at the same time.