Ok, I have come to set the record straight, but fear not, I am a nice person.
Basically both the full versions of PowerDVD 3 and 4 comes with *.ax directshow filters, these are automatically registered to enable you to play DVD content via Media Player. If you have more than one DVD player installed, the directshow filters may conflict and only the fittest will survive.
(See Darwins Theory Of Evolution)
Anyway, my best suggestion is to remove all traces of PowerDVD, uninstall, delete the directories, and remove Cyberlink from CURRENT_USER and MACHINE in the registry.
Try playing a DVD in media player, if it works, or tries to worl... you still have filters installed and need to find out what they are and remove them. If you get a message saying no valid codecs available you have no DVD filters installed and you can skip the next bit.
(((SKIP, HOP & JUMP START)))
To see what DVD filters you have installed, I recommed that you go to
http://www.inmatrix.com and download ZoomPlayer, attempt to play a DVD and when it starts right click on the screen and select filter properties, this will let you know whats up.
(((END SKIP HOP & JUMP)))
Now reinstall PowerDVD 4, hopefully it will work.
ok, just gonna switch quickly to another one of my multiple personalities, the suggestions guy.
DVD ERROR
ERROR CODE: 80A50000
I think this error may be caused by lack of ASPI layer, I noticed that PowerDVD 3 comes with an ASPI layer, yet PowerDVD 4 does not, however you can download one from the downloads section.
Try updating all your graphic card drivers, this can make a big difference due to the overlay which sometimes like to play up.
ok I'm done, flame me.