1000w?

My friend just gave me a 1000w HPS light. He got it from a greenhouse that he was doing electrical work in. The thing is HUGE has a round hood that is about 2' across at least LOL Will this light work for me to grow and how big of an area will this cover. It only has a small bulb in it now so what kind of 1000w bulb should I get since I got it free I figured I could get the best bulb available. Any help would be appreciated