Step 1 - At the Linux Boot Menu type "root=/dev/sdb". Do not change the boot menu selection (leave it on the top option), just start typing and the text will start appearing on the boot options line at the bottom of the screen. Then hit enter and the system will boot.

Step 2 - Edit /boot/grub/menu.lst to replace "/dev/sda" references to "/dev/sdb".

Step 3 - Edit /etc/fstab to replace "/dev/sda" references to "/dev/sdb".