System restore should get them back. But you'd lose Media Center. Can't imagine why you lost the tiles by installing Media Center. After the restore, you could try installing Media Center again, but who knows what will happen the second time--presumably the same thing unless Media-Center installation was not the actual culprit.
I found the problem. Some how the display property had gotten turned off. I was able to find the apps on the apps page and turn on the display property.