Olivier, FYI: your second link point to a non-existent page. It appears you have an extra "s" at the end of "software"
You can handle drag and drop by using the Windows API. As a quick way to get started I modified the example that comes with the Windows Message Queue library which you can download from NI. The primary reason for this is that it has a message loop. You can then tell Windows that you're going to accept drag and drop, and register for the WM_DROPFILES message. The DragQueryFile function will tell you how many files were in the drag, and you can then call it repeatedly to get each filename. Attached is the modified example (LV2009) to get you started. You will need to download the library separately from the NI site. All it does is display the dragged files to an array indicator. I also do not check to see where the drop actually occurred (i.e. to see if the user let go of the mouse on the tree control as opposed to somewhere else). If you need this I'll leave it to you to add it in.
Windows Drag Drop Example.vi