If you are lucky, it can be accessed under one of the removable panels for other devices on the bottom of the laptop like wireless adaptor or ram, etc. If not, you might have to do an extensive disassembly -- and it may even require (de)soldering. I would try googling the exact model number of your pavilion along with service manual like this example: dv3510nr service manual
Then you can find out where it is. You might even find a disassembly video on youtube for your laptop.