Tell him if he likes your computer over his slow ass computers so much to build his own new one and stop commandeering yours. It's not fair to you.
Quote from Yoorah;546522:
Why are you asking someone to lie to their father? O_o
Anyway, just talk to him and tell him that this bugs you. Explain to him that your computer is a very personal thing to you and that you'd like your dad to avoid using it since he has another computer he can use.
Basically this. But also explain that if it's a slowness problem with his computers and he really feels the need for a faster computer all the time, that he should really invest in his own rather than taking yours all the time, because
you use yours and would prefer to be the only one that uses yours because you do things that are important to
you on your computer, even if
he doesn't find them important - it doesn't matter. He should respect what is important to
you.
Explain how taking it while you're talking to friends would be like just grabbing the phone while he was talking on it, hanging it up and saying "Ah, well... You're not doing anything important. I need to use your phone for awhile." It's just rude.
And explain how closing your shop is detrimental to your game since it means you can't sell anything and can't profit and won't be able to provide for yourself in your game which you enjoy as a hobby, and you paid for and built your computer so you could do these things, and he's taking it all away for his own selfish reasons, when there's just no need for it.