Based on the description of the situation I'm guessing that the problem is not in the software, but in the DVD drive. Try looking at setting DVD region code.
Some licensed commercial DVD discs can arbitrarily change the DVD region setting without your knowledge.
Yes, but I am trying to watch the movies with VLC and VLC is supposed to ignore the region codes.
This is the first, what i hear. Which DVD make it?
I've never changed a region code in all my computer time.
I have, but that was ten years ago. Since then VLC has been able to handle all region cods without my changing the settings.
As to the DVD make(s) I have no idea. I've been trying to watch movies from several different companies. (With codes like 20903/ST/G1/RO and 8251592B-11/RO to mention two very different ones.) But they have all been Region 2 disks. If I can find a Region 1 disk I'll check i out.