I tried to download this a while back, but I went to the wrong websites and just got a virus. So I'm wondering; when would the best time be to download this? If my computer dies, will I need to download it again and if I didn't would it crash? Would it be safe to have it on an existing world? (if not that would suck) And do I need to get stuff like Buildcraft? It would be great if I could have some help.