pokertracker4 and holdemmanager2 trials through the respective sites are virus free . If you do a dodgy download off torrent to try and get an unlocked version for free you are highly likely to download trojans and other nasty software. Its not worth the risk. FPDB is a free hud but will take more effort to set up and get working. some pieces of software are banned by stars as they used a shared database and stars look for them . if they find them on your computer they can close your account. just stick to the main poker trackers.

snap poker on 888 is HUD free as 888 asked HEM and PT developers to remove support(although I think that snap tournaments are supported still but cash games are not) , so you won't find a snap hud .