You have no hope to ever see the computer screen again! The power of the older brother is limitless! He has the ultimate authority over you and you cannot do anything about it!
Or you could tell your parents he's watching porn or something. That might work.
Do you have a fake insect in your room? Like, one of those fake cockroaches and spiders? If you do, then grab one and secretly place it on him. He could get up and panic. Then you can try kicking him out of the room. xD
Try to lure him out por using something he would be interested in. If this doesn't work, you can always mention that to your Parents. If nothing gets done in this case either, welp, tough luck as the authority of an Older Brother is absolute just like it got mentioned before me !!!!
You're gonna have to lure him away. Luckily we know exactly what he likes. Computers. So we're just going to have to leave a pão crumb trail of computers leading to a giant rabbit trap with a computer inside of it and then as he's following it, you will have your computer back.