In Ubuntu at the grub screen of the Live CD press F6 and remove the words
quiet and splash with your backspace key. Then press ESC. Then Enter on
Try... This will allow you to see the text of the loading process and maybe
give a clue as to what is causing the problem. Once you know what it may be
then you can re-boot and try some of the options on F6. Use the space bar or
enter to put an X beside it. Try them one at a time to see if you can get it
to boot.

I suspect that it is a graphics card problem but it could be kernel panic
that is triggered by some hardware setting in the BIOS. HP does some funky
things with the BIOS. I have an HP desktop that has given me fits over the
years.