How do I reindex the Media Center Library?

I'm sorry if I posted this in the wrong group. Here is my problem. I
had all my media stored on an external drive that has now failed. So
now I want to use a different drive for my media.

The problem is that Media center is still showing icons for my lost
media and it is messing everything up. I told media center to stop
watching the folder that no longer exists, but the icons are still
there.

Could someone please point me in the right direction as far as getting
my media center library sorted out. Thanks in advance. TG