Windows 7 - My Laptop Screen Isn't working

My laptop screen is half black.

The display itself seems to have gone bad, you should replace it

but i dont understand i was simply cleaning the laptop from dust etc. before was working fine then i put the screws back in then this happen. it used to be just half of the screen but if you press on it with your hand it spreads it across. So are you sure if so could you find me a cheap 12" screen to buy.

Did you properly connect the screen cable to the board?
You probably wrongly re-connected some internal components

I never touched the screen cable i was cleaning the motherboard which something wrong could of happend. If there is something to do from the motherboard to the screen cable then maybe but could you send me a picture if what it looks like thanks

There is a connection that runs from the screen and connects to the motherboard, it differs from make and model of laptop, but if you examine the connections that are on the motherboard you should be able to find it. There could be some sort of documentation from the manufacturer of your laptop, they usually have a section in the manual called "Repairs and replacing parts" or something to that effect.

It is a Advent 9112 Notebook around three years old.

Hi Amirsad, have a look at this link Laptop Repair Help » Notebook display assembly diagram. How an image appears on the screen. It will give you a greater understanding of how a picture is displayed on a laptop Browse the site for more info on repairing laptops

Did the motherboard need cleaning

It's definitely a hardware issue, whether it's your screen having gone bad, (unlikely if it JUST happened and was working immediately before the cleaning, but still a possibility) or a connection that came loose, or screws being too tight and pressing on the display, etc... Take it apart, check the connections, and put it back together and see what happens.