How do I deal with an HP laptop with lost power-on password?

As MaQleod said - wiping the BIOS settings is the only way to go.

A few notes though:

Laptops often don't have a battery specifically for the BIOS but often either draw power from the main battery or use an EEPROM (flash memory) that needs no battery.

You can sometimes wipe the BIOS by removing the laptop battery and leaving the laptop unplugged for an extended period (I'm talking weeks here), but if the laptop's using flash memory that won't work.

The only other option is to locate a set of CMOS Clear jumpers / solder pads on the motherboard and join those together with a screwdriver / wire to try and wipe the BIOS. Finding it could be hard though.

I assume you mean bios password. In this case you will need to open up the laptop and pull the bios battery from the motherboard, usually a few minutes out will be fine to erase the bios and default it back to factory. Put the battery back in and you are good to go.