Test if it is HDD problem by taking out the HDD and see if BIOS screen POST is okay. If no problem there it should end up by giving you message that no bootable device detected.
Test with battery in and battery out, mains on, mains off etc. it might be a problem with either the battery or the mains connection.
To switch off safely, hold the on/off power button in for about 10 - 20 seconds until it powers down and switches off.