it doesnt find the root Filesystem because the UUID of the disc is wrong
You have two options:
1.) edit the root part directly in the bootloader grub. Replace UUID=123123..... with the right rootfs /dev/sdaX.
Once the system boots run update-grub
2a.) boot a Rescuesystem like grml or SystemRescueCd. If your System is 64bit boot 64bit kernel!
- mount the rootfs probably /dev/sda1 to /mnt
- then run the following commands to update grub
bash
chroot /mnt update-grub
2b.) If 2 fails you can reinstall grub with this:
- mount the rootfs probably /dev/sda1 to /mnt, then:
bash
mount --bind /dev/ /mnt/dev
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
chroot /mnt grub-install /dev/sda
I hope this helps
Tim