disk refit finds a previously deleted database that was partially overwritten by a subsequent create database or alter database. The dbid of the deleted database was not reused by any subsequent database creation.
Symptom: You see one of the following:
rows in sysusages with no matching dbid entry in sysdatabases, or
a sysdatabases dbid entry with corresponding rows in sysusages that show a numbering gap; that is, (lstart + size) for the dbid does not equal the lstart of a subsequent entry with the same dbid, but one or more rows exist with a greater lstart for the same dbid.
Corrective Action: Follow the instructions in "Queries to Find Suspect sysusages Entries" below. If there were usage gaps, be sure to delete sysusages entries and any sysdatabases entry for the dbid where the gap(s) exist.