I have a gateway laptop and when i turned it on the screen goes black and wont turn on. Its charged so i tried one more time and it came on but then turned black again but when i hold the power button on it stays on but when i let go it goes off!! i need help asap why is it doing that???????

Time to send it on a trip to the repair depot. Go online and get an RMA from Gateway. If it is under warranty, they should provide a pre-paid return label for UPS or FedEx or similar. If it isn't under warranty, then you will probably have to pay for the shipping to the depot, as well as the repair costs. Usually these are not excessive as they replace the broken stuff (motherboard etc) with rebuilt units and then rebuild yours to factory specs. The one thing you will want to do is either fully backup your hard drive, or remove it from the system before sending it in. You can back it up by removing it, placing it in a docking bay ($25-$50 USD), attach to another computer, and then copy the data. If you cannot access the data, then the drive is the failing component.

That dilemma can be sorted out at the repair shop, coz it seems to be a problem with the power button. It seems to have developed some problems.

Visit a repair shop. I am sure it will get fixed.