Using WMP--NOT Power DVD



I have a Windows Vista Home Basic and I have encountered a problem with
Windows Media Player. Every time I insert a DVD into the drive, the computer
automatically runs Power DVD to play the movie. If I run Windows Media
Player and then insert the disc, then the computer automatically shuts down
WMP and it runs Power DVD. I do not like Power DVD and I want to use Windows
Media Player. I have tried EVERYTHING, but whatever I do, the computer
automatically shuts down WMP and runs Power DVD. Please Help!!!
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Thank You
.