According to Microsoft note on installing Windows Media Player 11 and the eventual roll back to a previous version, you might not be able to do this if the hidden folder $NtUninstallwmp11$ is deleted from your computer, Microsoft goes on to say that "some non-Microsoft programs (such as CCleaner) delete this folder in an attempt to remove unwanted files from your computer".
I personally have had this issue of not being able to uninstall WMP 11, and after some trouble managed to finally find a workaround that solved the problem:
"Go to Start, Run then copy and paste this in:- C:\WINDOWS\$NtUninstallwmp11$\spuninst\spuninst.exe"
I would sincerely like to know if this is true and if so warn you about this issue so that it may be corrected in a future version of CCleaner.
Tks.