We are only aware of one library on the market for creating a namespace shell extension, and it only works with Delphi (VCL). We haven't evaluated it so I can only presume it works, here is the url:
http://www.shellplus.com/examples/na...-example.html. Ultra Recall is entirely written in C++ however...
If someone else is aware of a C/C++ library for a namespace shell extension, we would be glad to look at it. I can tell you from the research I've done personally that doing this from scratch would be an extensive project...