Try these steps :
1. Disconnect the AC Adapter.
2. Remove the Battery.
Note : Please see that there are no external devices or cables connected to the Notebook.
3. Hold the Power button down for 30 seconds to 1 minute.
4. Reconnect the AC adapter and do NOT connect the battery now.
5. Turn on the Notebook power.
If the Notebook doesnot start fine, we may have to need a Desktop monitor to check whether the issue is with the LCD, Graphic Card or the Motherboard itself.
Connect a Desktop Monitor to the VGA Port of the Notebook and press FN + F4 key to get the display on the Desktop monitor after the power button is pressed.
If you get the display on the Desktop monitor, the issue is with the LCD of the Notebook.
If there is no display either on the LCD or the Desktop monitor connected, the issue can be either with the Graphic Card or with the Motherboard itself.
Confirm if the Notebook is in warranty or not.
There are some known issues with few HP Pavilioin Notebooks installed with AMD Processors.
Try the link below and contact HP Chat Support if the Notebook is purchased in US to get it repaired for free :
Check the Product Number if it is listed among the once listed in the link below :
You can get the Notebook repaired for free if it listed among these numbers and is purchased from US.
Hope this helps...