Cannot delete priority category

I want to delete a priority category, but I can't because it is in use by a module. I get the following error message:
WARNING :Priority is being used by a module. Hence cannot delete it from database. But it has been marked as not for further usage.

I read the information here:
http://forums.manageengine.com/forumHome.do?forumGroupId=49000000002007&forumTopicId=
I used a database schema I had to substitute my table and field names in the queries. My queries did not work, and I suspect it might be because I substituted the wrong information. I used this query:
select * from prioritydefinition where priorityname='reserved for service manager'

Is there a current version of the database schema somewhere? Is there another problem I'm not seeing?

Thanks!