You cannot just drag and drop files from a DVD video disc (DVD-Video) and get a playable file. You need software to "scan" the VOB files and convert them.
If a DVD is skipping or failing to load, you may need a "surface scan" to check for physical degradation or unreadable sectors. Scanning Devices - AVG Business Help dvd scan
For catastrophic failures, command-line tools are superior. You cannot just drag and drop files from