Here is the grub site for errors and other helpful grub information; http://www.gnu.org/software/grub/man...roubleshooting
, you may want to boot to a partition tool CD to view all the partitions, such as this one here; http://gparted.sourceforge.net/
, and after booted either to a live Linux CD or USB flash drive, you run this; fdisk -l, as the root user, which shows all drives partitions, and you can copy and paste it as a text file to save and print it. Also real handy to boot to is this disk; http://www.sysresccd.org/Main_Page
You then may need to edit your grub boot menu file here; /boot/grub/menu.lst so that it boots to the correct one for your Linux. Are you dual booting with windows XP ?