Hi,
First do a hard reset, remove the battery and AC adapter then press and hold the power button for 20 seconds.Put just the AC adapter back in then power it on. If doesn't get pass the BIOS screen try removing the HDD off the laptop then power it on see if it gets pass the BIOS because if it does possibly that it's the HDD but put it back in and see if the same problem persist just to support that theory. Next is to reset BIOS into default by removing the CMOS battery then put it back in after couple of seconds (Note: Do this while laptop is OFF always). Lastly is to reseat the RAM, remove it and make sure that it's seated properly in the laptop.