1. Check the power. Make sure that the laptop is plugged in and that the power cord is properly connected to the laptop and to an outlet. You can also try using a different power cord to see if that resolves the issue.
2. Check the battery. If your laptop has a removable battery, remove the battery and then try to turn on the laptop. If the laptop turns on, then the problem is with the battery. You will need to replace the battery.
3. Check the power button. Make sure that the power button is not stuck or damaged. You can try pressing the power button a few times to see if that resolves the issue.
4. Check the BIOS. The BIOS is a small program that is stored on the laptop's motherboard. If the BIOS is corrupt, it can prevent the laptop from turning on. You can try resetting the BIOS to see if that resolves the issue.
5. Inspect the hardware. If you have checked all of the above and the laptop still won't turn on, you may need to inspect the hardware for any damage. This includes the power supply, the motherboard, and the memory. If you find any damage, you will need to replace the damaged component.

If you have followed these steps and the laptop still won't turn on, you may need to take the laptop to a certified technician for further diagnosis and repair.

Here are some additional tips for troubleshooting a laptop which won't turn on:

• Check the error messages. If the laptop displays an error message when you try to turn it on, the error message may provide clues about the problem.
• Try booting the laptop in Safe Mode. Safe Mode is a diagnostic mode that allows you to boot the laptop with a limited set of drivers and programs. This can help you to identify the problem if it is caused by a driver or a program.
• Create a system restore point. A system restore point is a snapshot of your laptop's system settings. If you create a system restore point before you start troubleshooting, you can restore your laptop to the point before the problem started.