[CentOS] Manually mounting partitions in "linux rescue" mode

I boot from the installation DVD, with an already existing CentOS 5.5 
system on my hard disks. I have separate boot, root, and home 
partitions. I have moved the boot partition and now I need to 
re-initialize grub from rescue mode.

Attempting to use 'rescue mode" to automatically mount my system under 
/mnt/sysimage eventally fails with an error message, which essentially 
says 'mount error' and nothing else. I am then put at a command prompt 
as root.

So now I decide to manually mount my partitions at /mnt/sysimage and 
then do a chroot to /mnt/sysimage. This succeeds and when I look at my 
files they are there.

I now try 'grub' and the 'grub' shell comes up. I now attempt the 'grub' 
command:

root (hd0,9)

only to be met with:

Error 21: Selected disk does not exist.

I do not know what this means and how I can correct it. Does anybody 
know what is going on ?

One thing I am concerned about is that when I booted from the DVD and 
was eventually put at the command prompt, I saw there were devices in 
the /dev subdirectory but after I did the chroot, there were no devices 
in the new root's /dev subdirectory although when I had previosuly 
booted into CentOS 5.5 on my hard disk off course they were there.

The other thing I noticed is that after the 'chroot' the 'mount' command 
showed only my root partition mounted on /dev/sdb8 where it actually 
exists ( along with sysfs and proc which I mounted from the old root ). 
But despite this there are no subdirectories under the new root's /dev.

I am just trying to re-initialize 'grub' so I can boot my CentOS 5.5 
system again. There must be a way to successfully do this from the 
installation DVD. If somebody can give me the steps to manually mount my 
partitions and succeed it would be very much appreciated.