I recently installed Ubuntu on a system with a slightly irregular hard drive configuration. Two SATA drives were running Windows on a mirrored (fake) RAID array, and a third SATA drive was ready to have linux installed. The Ubuntu installer recognised the drive as the third hard drive, and installed itself as expected, with Grub installed in the MBR of this drive, being first in the BIOS’ boot queue. However, all references in Grub’s menu.lst for the Ubuntu installation pointed to (hd2,0), which resulted in an “Error 17: Cannot mount selected partition.” message from Grub. The solution was simply to edit the entries to read (hd0,0) for (hd2,0) as Grub now recognised the third drive as the first on account of its place in the boot order.