Assuming that you have a legit licence, it should be legal to have Office installed on both a desktop and a laptop simultaneously if you're not using both at the same time. Actually, any reasonable software licence should allow that, though a few technically don't.
Installing Office, either X or 2004, is just a drag-and-drop operation; any necessary system stuff gets installed when you run it for the first time. (There are extra installers on the CDs of both programs for additional goodies, though). So, transferring between computers is the same. I have had reason to do this legitimately (it's a LOT easier than reinstalling all the service packs on Office X, for example).
If what the original poster was really asking about was how to preserve all his/her settings during the transfer (custom dictionaries, toolbars, whatever), then it's a matter of figuring out where Microsoft stores everything--somewhere in the ~/Library, no doubt, but I'm not sure where.