I had a similar issue with the T61 laptop. to solve it I wrote a small
appliction to switch the video output, and I looked at acpid how to
configure it to run this app when I press the hotkey.
the application in source code is at
https://bugs.launchpad.net/ubuntu/+bug/263887
to find out what button your HP has:
# become root
sudo bash
# stop acpid
/etc/init.d/acpid stop
# look at acpi events
cat /proc/acpi/events
# now press the button and you should see the magic line
# then press ctrl-c to abort the "cat" command above.
# and start acpid again
/etc/init.d/acpid start
look at the files in /etc/acpid/events/ and see which file
handles this magic line you have or write a new one.
the files are plain simple: one line "event=" with the magic cookie
and one line "action=" with the command to run.
good luck!
p.s. maybe give some feedback on that bug report page on launchpad.net
if it works for you, so they can fix your laptop too
