It's been 2 years since I've turned on OLPC. I'm looking to sell it, however the screen won't turn on. It's a black screen. It's plugged in and the battery led is yellow/orange (which I believe is charging and plugged in), and the power light is illuminated. What is going on? Does it need to be charged fully for the screen to come on? Thanks in advance for your response (which is desperately needed)!