Microsoft Indexing Service uses filters, much like FileLocator Pro extensions, to interpret given file types into easily searchable text. FileLocator Pro can use these indexing service filters, without the need to run the indexing service, to help convert files into easily searchable text.
The list of currently installed IFilters is shown in the IFilter settings tab. To use the IFilter activate it via the Enhanced File Search settings in the Options tab
A list of free IFilters can be found using a simple Internet search.