What do you mean it cannot find the partition? Does it show the drive with no partitions at all, or does it fail to find the drive completely? Is this just a single IDE/SATA drive, or are you running RAID/LVM? Does the kernel show anything about the drive being detected?
A bit more information would be helpful. All we know so far is that the system isn't booting properly, and there is a HDD you seem to be having a problem accessing.