Acer aspire 4520g cannot start

I am assuming it does this even if it is plugged into power supply. Try removing the battery and then re-installing it. Maybe it has come loose or has a bad connection. When the power supply is hooked up does it show that the laptop is charging? Have you left the charger on there overnight? Maybe the battery is really weak. It sounds like a bad battery to me but the only way to know for sure is to buy a new battery or test it with another good battery and see if it does the same thing.

Your description is one I experienced with an Aspire I had. I tried replacing the power supply but it turned out that the motherboard was defective. My warranty expired so I was out of luck in getting it repaired.

To try to correct this you should do the following: 1. Shutdown the computer, 2. Remove the power sources (battery & power adapter), 3. Press and hold the F7 key for about 20 seconds, 4. Put re-install battery, 5.Plug in the power adapter, 6. Turn the computer on.

This should reset your motherboard to factory settings which will recognize your battery and power adapter.

If this does not work, then call Acer for customer support. If you laptop is still under warranty, ship it to them for diagnosis and repair.