How do I housebreak a 4 year old italian greyhound?

Confine him to a small area until you have the problem under control. A dog will not usually go where he sleeps or eats. Take him outside for a walk after he eats. It will cause what's called parastoltic movement and will will need to releave himself. It will also be helpful to schedule his feedings about the same time and get him into a "rountine." Have you tried putting any of his droppings in the litterbox or on a puppy pad. They like to return to the same area to take care of their business. I know it might sound gross but also leave his droppings in an area in the yard you can easily take him to so he gets the idea. Good luck....if all else fails they make doggie diapers that will save your new floors until you get the problem under control.