Hi,
First, do a hard reset, remove the battery and AC adapter then press and hold the power button for 20 seconds and see if the laptop will boot up. If it doesn't work start with the RAMs, remove them off the laptop for couple of seconds then put them back in making sure that they are all seated properly. Next is to reset BIOS, remove the CMOS battery then put it back in and it should have reset BIOS to default. If all these won't work do contact Lenovo if it's still under the factory warranty for a repair.