said by TheSMJ:
In front of both the master bathroom (first pic) and entrance to the bedroom (second pic) you can see how the wood is much darker than the area to the immediate left/right of the doorway. The discoloration is much darker than how it looks in the pics, but you can still get the idea of what I'm talking about...
There are also small holes in the floor from where the carpet tack strips were nailed in, and a couple of ~1/4" holes drilled by a cable TV installer when he ran the coax up from the family room ceiling below (I'm guessing because doing a good job and going through the walls would have taken longer than 2 minutes). I'd like to think I could use wood putty to fill the holes, but I doubt they'd look right after staining. I'm not that worried about the holes, but if there was a way I could fill them in without replacing the boards I'd love to hear it.
You need to try to determine what finish is currently on the floor. My guess is either varnish or oil and wax. The darkening can probably be lightened or removed using wood bleach (oxalic acid). I use it on floor stains often. It may take several coats overnight or over days. finish up with a neutralizing rinse with baking soda. Personally I would not worry about the carpet strip holes. They are not noticeable once the room is furnished. To fix the drilled holes, you need to use plugs, do not use dowels. If you use a dowel, then there is end grain exposed. With a plug, the grain is the same as the floor.