One thing you might try is to see if your BIOS has a setting for type of OS, if so set it to Unix or Other. I had this problem on an old emachines with XP and Ubuntu not getting along. I'm not sure what the issue is with that, all the other computers i've ever had worked great. Just an idea, very well may not work. Grub is saying the disc you want to boot to doesn't exist if I remember correctly.. how is your HDD connected? Is it IDE?