Ruth,
Right-click Start, click Run.
Type optionalfeatures.exe and click OK.
Enable "Windows Media Player"

If the option is already enabled. it means WMP is installed on the computer. See if you can start WMP by running "C:\Program Files\Windows Media Player\wmplayer.exe".
If that doesn't help, uninstall WMP and reinstall it.
- In the OptionalFeatures dialog, uncheck "Windows Media Player" and click OK. You may be asked to restart Windows.
- After a restart, re-open the OptionalFeatures dialog and enable "Windows Media Player" and click OK.