I haven't tried this, but how about simply RENAMING the 'Windows Media Player' folder in C:\Program Files?
That worked for me in disabling Messenger (renamed MessengerNot). No problems. No boot complications. No more Messenger spam.
On reboot, I used Norton Windoctor and found and 'fixed' a dozen invalid links to Messenger during the boot process.
Not as elegant as uninstalling, but it may work for you.
Be sure you set a System Restore Point berfore you try this, if you do.
Hope this helps!