In KDE3x I was able to set the Hotkeys for starting applications both with keys on the main keyboard and the keypad (number pad). For example I had Seamonkey set to open when I clicked the "End" key on the keypad (num lock off).
Well KDE4 allows me to set the key but it doesn't work. Initially I thought the problem was that in KDE3 where it does work it is recognized as "KP_End" but in KDE4 it is recognized as "End". I verified in "share/config/hotkeysrc" how it was referred to in KDE3 and changed it in KDE4's "share/config/hotkeysrc" but still no luck. Sure I can do it on the main keyboard but that requires 2 keys and keypad only needs one.
I did a Google search but found nothing. I considered posting in the KDE.Org forum but it seems almost dead, only one reply to a post since November of last year.