How do you download old games specifically half-life and doom

Half-Life and Doom were created by big companies that still exist today so free downloads are illegal. You are advised to get downloads from steampowered.com where they cost only about $10 each. If you are a dishonest jerk then you are advised to get free downloads from thepiratebay.org. If you are lucky, your computer won't be overrun by malicious viruses.