A while ago I simply opened up my computer and this showed up;

(It didn't show up at Prt Scr, so I had to do one myself)
It's literary everywhere and I can''t get it away. Restarting the cpu doesn't work either.
Anyone with a helping hand?

Since pressing print screen doesn't show the black area, the problem most likely lies in your monitor. I personally can't help you with screen troubles, so you're on your own from there. However, I would recommend hooking up another computer to the monitor to see if the problem truly is your monitor instead of the computer.

EDIT: Judging from the fact that you can "Open Up" your computer, I'm going to assume it's a laptop. In which case you're going to have to hook it up to a different monitor and make the computer only use the hooked-up monitor. If your problem still arises while using the new monitor, it is 99% certain that something is wrong with your computer.

it's also possible that, if it's a laptop, you hit the duplicate/extend screen onto second monitor button, that does all kinds of weird stuff sometimes, try toying with that first

Hey, that's a Chrome theme like a Firefox persona. It's a background for the browser. You must have installed it from the Chrome Web Store. PS: you're on a foreign version of Google's website. Sounds kinda like French. A hacker took over my computer and streamed TERRIBLE heavy metal full-blast at midnight on my computer. Norton fixed it all up. I wrote about this on the Windows 8 VS Mac OSX Lion VS Linux Ubuntu discussion page. If you think this happened, check it. I'll look for a link.

Oh, I didn't see the side. Whoops. Looks like the hardware, wiring, monitor, or the settings have failed you/gotten messed up. Check all that and the settings.

@VincentV I'm sure Matillion, being from Sweden, is quite aware that the image posted is in Swedish.

Oh, Swedish. I didn't see. Oops.

Wow, hacker did that? Man I would of been worried for the speakers... Though I like some of that type of music.

I'm surprised Norton did anything! Glad to hear it got fixed though.

Well, I meant it made sure the hacker didn't install anything like a virus. As for turning it off, I did it, and you can be sure I removed the battery too. If there had been a virus, it could've booted itself back up w/ the battery. I guess the hacker was even lenient enough to stream the crappy music through instead of downloading it. Or maybe he was to impatient, or lazy. Whatever the case, I'm glad that hasn't happened again.
EDIT: And by mentioning the whole incident in the first place, which seems irrelevant, I meant a hacker could have messed around with the settings as a prank. Who knows what really happened?