When creating my form, I wasn't enough aware of the configuration for the default core description field. I don't want a summary field, but I did not pay much attention at that when setting my form in the past. Now, when I try to change the field options to remove the summary field, I get the message "There is data for this field in the database. The field settings can no longer be changed.". Is it possible to override this restriction and force the change?
I'm guessing the type is
Long Text with Summary. If thats the case, can't you just go to admin/structure/types/manage/
[your content type]/fields/
[your field name] and uncheck
Drupal will then automatically create a summary if it's required to, just as it would if you had chosen
Long Text (without summary).