Hello,
You can try a older version of the Knoppix to boot the PC.
You can also try the FCCU Gnu/Linux boot CD that is a remastered Knoppix (3.9) (
www.d-fence.be)
If it's not possible to boot the PC, you can try a boot with HD disabled in the BIOS and see if the HD is really the source of the problem.
You can try to extract the HD and connect with a adaptor to a other computer and try to acces it.
Good luck.
--
free_ouyo