In our preparation for upgrading from 2007 to 2010 we ran our pre-upgrade checker and it returned the following:
Information Only : Customized field types that will not be upgraded.
A field type using custom Collaborative Application Markup Language (CAML) in itsRenderPattern element will not be upgraded as an XSLT-based field type. Fields based on this custom field type will be rendered without any custom formatting in SharePoint 2010. The following field types will not be upgraded:
ContentTypeIdFieldType(Content Type ID)
What we want to know is what lists use these fields? We are trying to clean up these fields before the upgrade, and are at a loss as to what this means. We are trying to be pro-active about any problems we might encounter. Can anyone offer advice? Thanks so much!