Media Center 7 Sleep Timer is an awesome Media Center application (also works as add-in) to shutdown/hibernate your Windows 7 machine after a selected time interval.
Once you installed Sleep Timer, you can access it either from the Start menu or Extras Library in Media Center. The current version of Sleep Timer comes with five options: Shutdown in 60 minutes, Shutdown in 30 minutes, Custom timer, Shutdown at time, Monitor off, and Cancel timer.
The best thing about Sleep Timer is that you can customize almost everything from time settings and to the interface. You can change the default Shutdown in 30 minutes and 60 minutes options by editing the MC7 Sleep Timer Settings.cfg in the install folder.
You can also use the Readme file available in the install folder to know more about customizing the Sleep Timer.