Technically speaking, the only way to reinstall WMP11 is to reinstall the Vista system. This will reinstall all of the components of Vista, which includes the integrated media player. This can be a hassle, however, as this process can take several hours and may involve the loss of important settings and documents. Another option, similar to reinstalling, is to do a system restore. This will restore the settings of Vista (and its components, including WMP11) to previous states.