Is there a way of turning a computer into a Arduino type board?
A regular Arduino uses an AVR, more "pimped" Arduino might go to ARM. Some special versions of Arduinos uses other chips, such as the ever iconic ESP8266.

For home automation, an ESP8266 is WAY enough. Using an ARM is quite and overkill for home automation. But I've never seen anybody using a full PC for it. Why? Because it is around 10-20 times more expensive. They require much more components and many other things.

Something close to a full PC that you can get is a Raspberry Pi (any version would do). They act like a small PC, some even use it as a laptop. See PiTop. The Raspberry Pi is stronger, more powerful, and much faster then any Arduinos. The Pi also has ethernet, a graphic interface, and an audio interface built in. That means that you can pretty much connect it to a monitor and it will work as a normal PC running either Windows or Linux. You can then watch a video, with graphics and sound, from the inthernet without external modules like you would need on an Arduino. Their only weakness is that it is harder to program them to read may sensors. That is why the Arduino is popular for covering that.

At the end of the day, it is your choice. I would personnally suggest an ESP8266. This module has many GPIOs, depending on the breakout that you have, and has WiFi built in. This is a great feature for home automation. Most home automation builders use this module.

If you have any questions about the informations I just gave you, comment it, I'll reply.