Windows Media Player comes bundled with Windows OS and it can't be uninstalled. If you want, you can disable it. For this purpose, navigate to Start > Control Panel > Uninstall a program, open Turn Windows features on or off window, expand the Media Features list, un-check the box next to Windows Media Player and click OK:
In order to solve the problems, I suggest you disable the player, reboot your computer and enable it again. If you still have issues, try to update it to the latest version.