Hi @erosaxie
Try a full power refresh and check if that resolves the problem:
a). Perform the ''battery safe mode'' procedure as shown on p.30 of the [http://h10032.www1.hp.com/ctg/Manual/c05271036.pdf|maintenance and service guide] for the laptop.
b). Disconnect the battery from the motherboard (see p.61)
c) Remove the RTC coin cell battery from the systemboard (see p.70)
When the RTC battery is out, measure its voltage. If it is <2.5V DC or >4-5 years old, replace it. The battery model number is on the battery itself e.g. CR2032 perhaps.
d). Reinsert the RTC coin cell battery and reverse the above procedure to reassemble the laptop.
Once the laptop is completely reassembled, connect the charger and check if it turns on OK.
If it does there may be a message stating that the Date and Time are incorrect. This is normal as the BIOS has been reset back to its default factory state. Once the Date and Time have been corrected, the message won't appear the next time the laptop is started. Also any user definable BIOS settings that were altered by you to suit whatever system requirements you needed, will have to be changed back again too.