when people did not like hardwood flooring and did everything possible to cover it up. It was thought to be cold, slippery, and hard to maintain.
well, times have definately changed. We love that beautiful wood grain look of a hardwood floor and doing everything to bring it back to life.
I am assuming that you have pulled up the carpet and now you see the plywood. Is the ply wood screwed or nailed down? determine this and undo the fasteners in its respective manner.
If the flooring is blemished or stained or whatever, you can repair it because I am sure its made from thick real wood that can be heavily sanded and brought back to life via sanding and staining and sealing.
The nail holes can easily be fixed, but I would pry those nails or screws up very gently and avoid any damage.
Now, if worst comes to worst, you can always lay back the ply wood if the hardwood is way beyond repairs.
Your home will take on a new ambiance with maintained hardwood flooring and you should give it a good try.