Click on this link:
[link|https://www.manualslib.com/manual/741403/Hp-2000.html|HP 2000 Service Manual|new_window=true]
To reset BIOS to defauls:
Go to page 39 (''manual's pages as on bottom of page'') to see how to remove the main battery.
You will now need to read through the manual on how to get to the RTC battery.
Page 72 for disconnecting the RTC (CMOS) battery.
Press power button to release all stored power on system.
Reconnect RTC battery.
Reassemble computer.
Reconnect main battery.
The laptop should boot now.