Just install it on the new laptop. Install the applications to the system drive, and use the external drive for your media and render directories. You don't mention what version of Liquid you're runniing, and there may be issues when trying to re-activate associated applications like HFX Pro and TDK Pro. If installing on Vista or W7, there's a procedure published at the top for how to do this. If you've problems, let us know.
Good luck.