Steve is having issues where his computer turns back on after he shuts it down. Leo says to look in your settings for "wake on LAN" and turn it off. It's a feature designed for IT networks to be able to turn on the computer remotely. You also want to be sure everything is shut down. There may also be a scheduled wakeup. Both features are in setup (BIOS). Turn on your computer and his F12. Once in the setup, go through the settings for those options and disable them. Could a hacker be turning it on? Leo says once it's shut down, nothing is running. So no, it isn't that. There's something in the BIOS/Setup that is waking it up.
There's one more thing called "reboot on power loss" that could be waking it up as well.