Didnt use my HP Pavillion notebook for a couple months and now it won't start up

i got an HP Pavillion Notebook a few years back and i stopped using it a couple of months ago. Today i decided to plug it back in, and when it was fully charged i tried starting it up. When i pressed the power button, the lights went on and the fan went on. literally a second later the fan went off and the lights remained on but nothing came up on the screen and the computer didnt do anything. i can open the cd rom drive but other than that it doesnt do anything at all. I’ve tried unplugging all the power stuff and plugging it back in, ive tried using a paper clip to do that little power reset thing, ive tried taking the battery out and putting it back in, but whenever i hit the power button the same thing happens. I wasn’t having any trouble with the computer before i stopped using it and i dont see what could have happened to it between now and then since it hasnt been moved at all. I’m thinking that theres a possibility that the battery is dead but if it is then it doesnt make any sense that the battery power light is now yellow (its orange when its still charging and turns yellow once its fully charged). If anyone knows what might be the problem and can offer a possible solution i’d be greatly appreciative, thanks.