What happens when you try to open the media center? What is error (if any) you are getting? When was it last working fine? Have you done any changes to the computer?
I would suggest you to disable and then enable windows Media Center on expanding Media features from the Windows on or off features option and check if this resolves the issue. Refer the below link to view the window for disabling and enabling windows media player - http://windows.microsoft.com/en-US/windo…
Also check, if you are getting any errors in the Event viewer and if you are getting any, do provide us the details. To open event viewer follow the below mentioned steps:
1. Click the Start button then click Control Panel in this click System and Maintenance.
2. Now click Administrative Tools, and then double-click Event Viewer. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
3. Click an event log in the left pane.
Double-click an event to view the details of the event.