You'll have to write a shell extension. From what I can tell, it can be done in .net 4.0 now (although it's still recommended to do it in unmanaged code). Here's an example provided by micorsoft
. It's not beginner level stuff, and the example provided is C++ - fair warning.
If this is the first time you're reading the term "shell extension", then you might have a look here: The Complete Idiot's Guide to Writing Shell Extensions
. No offense intended - that's just the name of the article. Good luck.