Here's a possible fix. I had the same problem with Knoppix 6.4.4 on a Compaq Presario. It appeared that the system lost track of the DVD drive and would only look in /dev/sda1 and /dev/sda2 . The fix for me was to add the noapic cheat code at the boot prompt, then it found /dev/sr0 and booted. So try boot: knoppix noapic