You would use this command to find out the UUID of the device in question:
Then you need to delete the /dev/sdX part(s) from both /etc/fstab and your grub menu.lst and replace with the proper UUID.
You could also use a label. If you use ext2/3, you would use:
sudo tune2fs -L device_name device
for example, sudo tune2fs - L Ubuntu_sys /dev/sda1. This will name the partition Ubuntu_sys, just like you can give windows partitions a name. Then it's the same procedure as above, remove the /dev/sdX from /etc/fstab and boot grub menu.lst and replace with LABEL=Ubuntu_sys. Do NOT do this on a mounted system!