OSB won't hold a nail, use plywood or solid wood under hardwood flooring. Some guys use glue over osb, but still not as good. When I did my oak flooring, I laid on the diagonal, and put screws in the plywood first to get rid of squeaks. Even in spots the screws didn't help, the oak doesn't squeak. The house was about 20 something when I laid the oak. Had a few squeaks under the carpet. Don't notice any now.
