This should provide you with a walk-through:
Use Shell Context Menu in your applications[
^].
Note some things: it has nothing or almost nothing to do with "extra Windows memory"; I have no idea why you consider these concerns related. Right term for the menu is "Context menu". Prefer disabling of the items to hiding them. No, it will affect not just the Windows Explorer but any file manager or any other code based on Shell API — be aware of it. Some file managers will have different commands added to the Context Menu, like "Move" in one step. There are many other ways to manipulate file, using the console, first of all. See also the notes by Nishant he posted in his Solution.
That said, if you think your Context Menu can provide some kind of file protection, think again: it won't, whatever you do with the Shell.
Finally, I'm not sure you really need to do this work (unless you want to register really serious application to work via Shell interface; a very successful example is such approach is TortoiseSVN,
http://en.wikipedia.org/wiki/TortoiseSVN[
^]).
If a Word document is opened, it cannot be deleted/moved anyway as Word keeps it open without shared access. If you simply use Word automation, it will always behave like that. In all other cases, you can do the same.
—SA