I agree with Ailwyn.
If you want to get stuff from torrent sites, be aware that there are plenty of to$$ers out there who will give you viruses at the same time
You are best getting torrents which are .avi files, not .rar files, but sometimes there is little choice as to the format.
I use a program called 'extract now' (free from
www.download.com) to decompress my .rar and .zip files - and i always decompress them on an old laptop where i can re-boot if worst comes to the worst - but generally, if you run antivirus though the .rar files it will pick up any 'nasties' before they can do any harm, and then run it through the uncompressed files before loading them into media player.
PS - there is more chance of a virus on 'dodgy' downloads (Porn/unreleased films/new software titles) than from a TV series, but it is worth getting downloads from a reputable uploader and/or reading comments left by other users - as a general guide, the more seeds there are, the more reputable the media is likely to be.