Hi there,
Model number, model name, operating system, 32 or 64 bit?
Have you tried connecting a USB keyboard to check it if it's the board at fault here?
If your laptop battery is removable-
Try this:
Shut down the notebook
unplug the AC Adapter
Disconnect all the external peripheral devices
then remove the battery
Hold down the Power button for 30 seconds
Re-insert the battery and plug in the AC Adapter
Tap away at the esc key with USB keyboard as you start the notebook to see if this will launch the Start-up Menu
then select F10 to enter the bios menu
Press F5 to load the defaults ( this is sometimes F9, but the menu at the bottom will show the correct key )
use the arrow keys ( assuming they work in this menu ) to select 'Yes' and hit enter
Press F10 to save the setting and again use the arrow keys to select 'Yes' and hit enter.
Boot into Windows, let it load, check.
Note: If you find the keys don't work in the Bios menu, then this is likely to be a Hardware issue.
Test for hardware issue from BIOS System Diagnostics by pressing F2 or F10 soon after restart - do component test - keyboard test.
This may be of help-
http://h10025.www1.hp.com/ewfrf/wc/document?cc=uk&lc=en&docname=c03738933
If troubleshooting doesn't work, it's probably hardware issue, you may Contact HP in your region if so.
Thanks,