I was chatting to a person the other day and they wanted to know how Windows Desktop Search (WDS) indexes different file types.
Specifically I was asked if WDS handled this in a different way to popular search applications like Beagle. Fortunately the answer is simple. WDS uses plug-ins called IFilters to support file types. For example in order for WDS to be able to “understand” an Adobe Acrobat file you would need to have the Acrobat IFilter installed on your machine (installed by default when you install the Adobe Acrobat reader).
For more information on how to write an IFilter there is some great information available at http://addins.msn.com/devguide.aspx#AddingaNewFileType as well as a very comprehensive article located at http://channel9.msdn.com/wiki/default.aspx/Channel9.DesktopSearchIFilters.