I know that you have asked the question before, and as far as I know there is no registry hacks that allow mapping of the buttons. Why are you trying to avoid installing AEButton Plus? Cost? Memory footprint? .....The memory footprint is ~120K and it is practically free. There are other alternatives. They are talked about in the thread
Are there really no way to truly close apps with the "OK" button?.
Hbutton allows mapping of the 5 keys but not the ok/start menu.
HandySwitcher also allows mapping of the OK button.