If you booted from the live Knoppix CD, then I think there is a good chance that the hard disk is failing. Download the utility from the hard disk manufacturer (most likley Hitachi) and run it to see if you have a faulty hard disk.
http://www.tacktech.com/display.cfm?ttid=287
Another thing you could try is installing Knoppix, if that fails, then you can be pretty sure it is the hard disk.
http://www.tacktech.com/display.cfm?ttid=287
Another thing you could try is installing Knoppix, if that fails, then you can be pretty sure it is the hard disk.