I saw someone ask about this one time, if this has been answered then I'll lock it.
I had this problem recently, I got a new keyboard and mouse for my laptop, now 'uh oh' I picked 2 button mouse and laptop keyboard! Well instead of going around changing all the controls back, I looked around and found this:
Go into options,
Go under controls,
Hit "Defaults>>",
Here you can change the mouse from 1 - 3 button, and keyboard from num pad-less to regular.
Hope this helped.