It's a program that's actually used to map things like MIDI controllers, Wii-motes and PS3 controllers to actual keyboard commands, but naturally also works with regular keyboard remapping!
Note: It looks scary when you run it, but under View you can set it to GUI. There you can set it to Manual and change your Output Device to Keyboard. Then you just remap the regular 1-0 with your Numpad version.
Here's how the help file describes it:
Start up PIE. Choose the "File" Menu,
then click "New". This will clear
whatever was in the big white box so
you can type your own script. We want
the W key to be controlled by the up
key so type this on one line then
W = Up
This is a working PIE Script so you
can test it by choosing the "Run!"
menu and clicking "Run".
Whenever you press the up arrow key
(on the cursor pad, not the numeric
keypad) it will type a "w". Try it
out! This will work in any program.
Note that it will still move the
cursor up. The Up arrow key still has
its original function, but it emulates
a w at the same time. Try holding down
shift and pressing Up. It will type a
capital W, unless capslock is on.
Unlike the real "W" key, holding down
the Up arrow will only type a single
Now chose the "Run!" menu and click
"Stop". This will return our keyboard
Now do the other keys like this:
A = Left S = Down D = Right
(Don't worry if the S is orange, that
is because S is also an abbreviation
Save your script as Tutorial1.PIE by
chosing the "File" menu then "Save
As...". And run it again. Stop it when
you have finished playing.