Really confused

I thought I knew about torrents, but I don't understand this at all. Half-way through extracting a rar archive it said I ran out of memory. I already downloaded the torrent so I don't understand what is taking up more room. I'm just extracting the files, why do I need to clear more space? Can I delete the torrent after unraring and still have the video files?

Please explain what your usual routine is when downloading a movie or something by torrent.

P.S. It was a 20GB torrent for which I had 25GB free space, and I just cleared another 10GB. Will that be enough room or do I need another 5 GB or more?

 

Wow that's real helpful thanks. Not even willing to tell me what rule I've supposedly broken. If it's the P2P thing, I already knew about that, and from what I understand and have seen, that doesn't apply to torrents. Considering how popular they are, it seems they would have mentioned them as an example instead of a few Kazaa-like programs.