Most likely the report is connecting to it via an odbc connection. If you did not set up the connection you should be careful not to undo it when looking at it.
In Crystal, if you go to the ‘Set Datasource Location’ from the Database menu you can look at the properties of the .ttx file, it will tell you the Database Type. If it’s ODBC you most likely have the .ttx file in a folder somewhere with a schema.ini file that defines the column(s).