I have an FC5 system with dual boot to XP. I just copied the partitions to a new drive moving from an 80GB to a 240GB. The partitions have copied across well, but the names have changed.
Old layout was
/dev/hdb1 - ntfs and XP
/dev/hdb2 - /root
/dev/hdb3 - /
/dev/hdb4 - swap

New layout
/dev/hda1 - ntfs and XP
/dev/hda2 - /root
/dev/hda4 - /
/dev/hda3 - swap

I have grub installed and dual booting is working, but when the system goes to change from initrd to / it gets lost and Kernel Panics.

So where is the file with the definitions of what is attached to what. It used to be /etc/fstab, but that now reads like this with no hardware information.
LABEL=/ / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
devpts /dev/pts devpts gid=5,mode=620 0 0
tmpfs /dev/shm tmpfs defaults 0 0
proc /proc proc defaults 0 0
sysfs /sys sysfs defaults 0 0
LABEL=SWAP-hdb4 swap swap defaults 0 0

Please post a copy of your /boot/grub/menu.lst.

You'll need labels on the new partitions.
Stupid idea IMHO.

And the kernel line on your menu.lst will need looking at.

the system is well backup before starting this upgrade and
it is a non critical box.

/boot/grub/device.map
# this device map was generated by anaconda
(hd0) /dev/hda

/boot/grub/grub.conf
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,1)
# kernel /vmlinuz-version ro root=/dev/hdb3
# initrd /initrd-version.img
#boot=/dev/hda
default=2
timeout=15
splashimage=(hd0,1)/grub/splash.xpm.gz
hiddenmenu
title Fedora Core (2.6.20-1.2312.fc5)
root (hd0,1)
kernel /vmlinuz-2.6.20-1.2312.fc5 ro root=LABEL=/
initrd /initrd-2.6.20-1.2312.fc5.img
title Fedora Core (2.6.20-1.2307.fc5)
root (hd0,1)
kernel /vmlinuz-2.6.20-1.2307.fc5 ro root=LABEL=/
initrd /initrd-2.6.20-1.2307.fc5.img
title WINDOZE
rootnoverify (hd0,0)
chainloader +1

Well, your menu.lst looks OK to me. Maybe you should reinstall GRUB on the disk's MBR. The copying program you used may not have written it to the MBR properly. Just a thought???

I agree with syg00 you'll need to add labels to your new drive. The commands e2label or tune2fs will take care of this for you. If hdb is still around make sure to remove the labels from those partitions before starting on hda partitions. Your /etc/fstab will reappear once the labels are back in place.

I find it confusing that you listed hdb2 and hda2 as /root. Is that correct or should it be /boot?

Bill