Itunes TV Show season downloads versus individual episodes

I purchased several seasons of a TV series and my problem is when I go to watch the most recently purchased season, all the other seasons download as well which is chewing up my hard drive big time. How do I download just one season of the purchased show?

Also is, is it possible to download just one episode of a season as opposed to the whole season?

Please note, I am running itunes mostly off my windows laptop.

Thanks for the help