If you are going to be putting in serious miles walking (speed walking) or running... I would suggest that you go to a store that specializes in running and get fitted for a pair of proper shoes.
Take your old shoes with you so they can see the wear pattern on them.
Good luck! Have fun on the treadmill.
"Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather, to skid in broadside thoroughly used-up, totally worn out, and loudly proclaiming: WOW WHAT A RIDE!!!!"