If you want uninstall Windows Media Player 9, follow the next steps:

1. Open the Command Prompt. Go through Start -> Run and type cmd and press the OK button.
    
2. On the command line fill in the following line of code: rundll32.exe setupapi,InstallHinfSection InstallWMP7 132 c:\windows\inf\wmp.inf (see picture 1).
   
   

   Picture 1

3. Now just install whichever version you want.