Content Type is still in use error

I spent an hour trying to delete a content type through the SharePoint 2007 UI with no success. I kept getting an "Content Type is still in use" exception even though I had deleted all layout pages that used that content type. I even went as far as de-activating the feature that installs the layout pages in the first place.

Finally I figured out that I have to remove the content type from any document library that contained any of the layout pages attached to the offending content type.

In my case, I had a publishing web site. So I clicked on "View All Site Content" and selected the Pages document library. From there, I went to the Settings page and, under the Content Types section, clicked on the content type I wanted to remove and deleted it.