My wife and I just bought our first house with original 88 year-old hardwood floors in them. The current owner has refinished them and most of the floor is in great condition. Unfortunately a previous owner did not take very good condition of the floors and there are large dark stains in various areas. Both a friend of ours and our realtor said they think it is discoloration due to the sun. Here is a link to a picture of what's probably the worst area:

Is there anything that can be done to get rid of these spots?