The OS is tied to the machine. You can install in on the other and use something like http://www.alohabob.com/ to move the rest.
Is there a method whereby I can transfer the complete contents of the HDD on my old desktop, including the OS (Windows XP), to my new notebook without re-installing all my applications from original media and data files from a back-up? That would be a big time pain, since many of the programs have been updated with patches and such, which obviously won't be on the CD versions. If there is a way, what would I need to do this; cable, software, etc?