AVG (free but i dont like it)
norton 360 (costs $$$ but you can download it for free from a bit torrent client like vuse)
virgin safe guard (free and fast and good quality)
microsoft one care (i think you can download it for a 3 month trial)
If you use a torrents, then before you download them you should have a bit torrent client that says if it is safe/fake/or vius and has comments