On my old PBG4 Aluminum model there was a number pad integrated into the keyboard. The "5" on the number pad was the same as the "I" key, and the other numbers surrounding it, so the 7, 8, and 9 on the number row were also 7, 8, and 9 on the numpad. Also had keys like 0 which was the "M" key where it would be on a number pad too. The decimal also was used with the period key. I thought it was kinda hokey at first but when I actually used it (and yes I do use the numpad) I found it to work pretty well. You would access the numpad via a numlock key which was F6.
I don't know why they removed this from the newer laptops? It's not like those keys needed to be reserved for other special uses. Just another one of those cool little touches I kind of miss about my old laptop. Can't complain about the new one's speed and battery life and size though!