My Lenovo G560 ring something like an alarm after switching it on

Solution
You can look up beep codes on the laptop vendor support site.

Usually a really loud annoying sound comes when the battery is critically low but can at least power up the system a tiny bit.
Hi,

Does it still boot up or load into Windows when you power it on or does it just stay on a black screen? Please do try these troubleshooting steps that may help.
- Start by doing a hard reboot, remove the battery and unplug the AC adapter then press and hold the power button for 20 seconds then try booting it up again.
- If this will not work, do test the AC adapter if it's working properly. Remove the battery and power the laptop with just the AC adapter connected and see if it will boot up or not. do also try a different AC adapter that has the same voltage and see if it will work or not.
- Proceed with reseating the RAM's if trying a different AC adapter will not work, remove them all for couple of seconds then put them back in making sure everything is seated properly.
- If it will still not work, connect an external monitor and see if you'll get any display from it. If there's a display on the external monitor that could mean that the problem is the built in display.
- But if there's still no display on the external monitor that means the problem lies in the motherboard.