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I am sorry to inform you that this is a hardware problem and will require a service in order to be fixed.
Please, check the official article and you may find out what exactly is the problem depending on the way the LED light blinks >> http://support.hp.com/us-en/product/hp-pavilion-g4-1100-notebook-pc-series/5082220/document/c0173267...
You may have to bring the PC (or shipt it) to HP Authorized service center. If the computer is still under warranty, you will need to notify HP support first. If you are not sure where such a center is located, please contact HP support for assistance in finding one. Here is more info:
Hope this helps you.
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I am not employed by HP Inc. I express personal opinion only. **** HP Expert **** I work in IT and cyber security