I developed a site content type inheriting from Form in SP 2010 as a feature.
I associated the content type with a form library and later decided to
republish. I deleted the Form library and when trying to delete the content
type, it gives me the famous SP 2007 error:
The content type "XXX" is part of an application feature.
It is a site content type on a blank site, so there is absolutely no possibility
that this content type is used else where. I have deactivated the feature, even
uninstalled the solution but I am always getting the same error when deleting
the content type.
I queried the content db and found that my deleted forms library instance is
still there in All Lists table. I have already spent 10+ hours on figuring out
why my form library is not deleted. I have tried on more than one sites and
always able to reproduce the issue.