How Do I Know what OS I have

just bought an mpc1000 old blue....works fine tring to get the pad upgrades, just cant find them.
Now i am reading about different operating systems?
whos the best, where do I get it?
how much is it?
seems there is no easy fix, but I lov ethat I finnally have it...learning curves and all!!!
ps where do i get the pad upgrade, because i am on mpcstuff's "waiting list"
how long is it going to take!!!!!???
thanks

damn totally forgot

its like pad 9,10,11,or 12

i think..


hit mode and press all pads till u find it.
its there though.