My wife and I just moved into a 1940s Vermont home with great potential. We knew that there were beautiful oak floors in a four-season sunroom hidden underneath a green shag carpet. But after we moved in and pulled up the entire carpeting we noticed that the flooring had dark spots in several corners. A friend said that this was probably due to urine from pet accidents. We want to refinish the floors, but will these dark flooring stains ever come out?