|If the lock screen is there but isn't going past that it might be something like over heating or maybe a bad hard drive--something that's causing the system to lock up. If absolutely nothing is showing on the screen it could be almost anything.|
The battery and charger seem OK since it's powering up. If the screen is blank does it seem as if it's illuminated in any way?
If you have any USB devices connected, disconnect them.
If you feel up to it open the laptop's plastic cover over the hard drive and remove it. Then start it up and see if it acts any different.