I don't have
PowerDVD but some programs don't do a clean uninstall.Either they leave behind some of their own .dll files or take their .dll & don't replace the original .dll.It can be other files but is usually a .dll .
I had a software Avi2Dvd the cause WMP 11 on Vista to not play certain .AVI files.Fortunatly it uninstalled correctly.
You might try the Vista error checking to see if it will replace or repair the original .dll.