Drag&Drop works in IDE but crashes in EXE

VS6.0 ClassWizard filters messages list for several types of classes (frame, dialog, etc).
For example, dropping files in a dialog has generally no much sense so, if your class is derived from CDialog, most possible WM_DROPFILES is missing from the list.

However, it is also possible you really have to do that, let's say drop an image file in the dialog's background (just an example).
This case, you have two choices:

1. Manually map WM_DROPFILES as already discussed and of course, again, beware of handler signature!
2. Prevent ClassWizard from filtering WM_DROPFILES message, as shown in this FAQ: How to show all messages in ClassWizard list?