Hi fritzifu
The file that is opened when you double click a DVD is VIDEO_TS.ifo
This means that PowerDVD is set to open IFO files - you need to change that file association . . .
Browse a DVD in Windows File Explorer
Find the Video_ts.ifo file, right click that and choose 'Open With' - Choose Another App
Important - Check the box marked 'Always use this app to open IFO . . .'
If VLC Player is not in the list, scroll to the bottom and click 'More Apps'
Again if VLC Player is not in the list, at the bottom, click 'Look for another app on this PC', then navigate to find the VLC Player executable . . .