I just bought a house to live in. It was built in 1912 and smells like an old house and then there is a dirty, nasty smell, not mold, not death (but close to it). I steam cleaned the carpeted areas. I don't think it was there. The carpet smells like dust a bit and the water in the steam cleaner just smelled dirty. The large living room has new vinyl flooring covering old pine flooring. Could the old wood be harboring odors? The pine flooring is present in the downstairs closets and upstairs bedrooms. It doesn't smell bad there, just old.

Yes. The floors could be part of the source for odor. Pine is going to take in and retain odors more than hardwoods will. Do the pine floors have any sort of sealing coat on them? If not, you might want to consider putting a finish on them.

Is this home located somewhere that is hot and also has a lot of moisture? I notice that you say in your profile that you are located
Where it rains too much!

Please try opening the windows and doors and just airing the place out some. You could also place fans in the windows and doorways to help blow out the stale air. Air that has been in a certain place for a long time does tend to get stale.