HOW DO I IMPLEMENT AN INTERFACE?

Do you know how WinZip makes it possible to drag files into zip files and launch it? Or how it monitors when files are dragged into folders and knows the path to which to extract them? This is because it registers a shell extension dll in the registry for 'files' of type .zip and folder, directory, etc. Take a look, if you want, under HKEY_CLASSES_ROOT.
The way to implement a shell extension, (you can see articles about this on MSDN), is to write a dll that explorer can load that 'extends its capabilities'. To create a DLL that extends drag&drop functionality in explorer, I will have to implement two interfaces: IPersistFile and IDropTarget. How can I implement these two interfaces?
What I want to happen is the following: I want my program (or dll) to be notified whenever someone drops something on a file of type .zip . I also want to be notified whenever someone drops something onto a folder. By "notified", I mean that I want some method of my dll to be invoked with the appropriate PATH or FILENAME for me to act on, or at least my program to be launched with the right command line parameters. But for this, says, MSDN, I have to implement those two interfaces. My question is, HOW?

Please, if you would be so kind, could you also e-mail me a copy of your reply? My email address is [email protected] .

Thanks a bunch in advance,
Greg