Mayday Mayday, Ubuntu killed by M$

[LinuxMurah.com]

I've try this:

1. boot ubuntu install CD and choose boot:rescue mode
2. mount my / partition
3. #grub-install /dev/hda

and here is what I get:
'could not find device for /boot: not found or not a block device'

my partition table is:
hda1 : Windows
hda2 : /
hda3 : /cache
hda4 : extended
hda5 : /home
hda6 : SWAP

why still I cannot do grub-install?