If I understand correctly, and thinking about Lands of Lore, I suppose you want to bind the "W" key to the "8" on numpad event, meaning that pressing the "W" key you want to go forward in game.
Well, if this is correct, you should follow these steps:
1) Open the key mapper (Ctrl+F1).
2) Choose the event you want to bind to another key in the virtual keyboard and click on "Del". Now the event is not bind to any key.
[i.e. The up arrow ("key_up" event).]
3) Click on "Add" and choose the key you want to bind to the event.
[i.e. The "W" key to bind it to the "key_up" event.]
4) In the virtual keyboard, click on the key you've just chosen in step 3 and click on "Del" to unbind its default event, otherwise it is bind to two different events (its default and the one you added above).
[i.e. Click on the "W" key and click on "Del".]
5) Repeat steps 2 to 4 to change others key/event bindings.
6) Click on "Save" when done.