Laptop Booting Problem

Good day, please can you help this computer novice out. I bought a HP Pavillion last Thanksgiving and it has been great until yesterday. When I wanted to use the laptop today afternoon, it refused to come on although it blink a light to show it was receiving power. I thought it was power problem so I connected it to a power outlet. I tried to start it, same thing as before. I reasoned that maybe it needed extra charge and left it for 7 hrs, nothing changed. Although it once started and reached where the blue screen which lists username and it turned off, but this was b4 the 7hr charging. What do I do. As of now, it is connectted to an outlet withhout the battery inside.