When installling ProE, the license looks for the cpu-id of the machine.
If you put it on an external drive and transfer from machine to machine, it wont find the original cpu-id. If you have floating licenses on both home and office machines, then you may be ok.
Proe looks at the network interface card ID so concievably one could move both the external drive and NIC to take the license with you. If you have floating license and can reach the license server you can run Pro/E from anywhere. WF2 also allows license borrowing, this is really designed to work with a laptop.
Be sure to install Pro/E with no spaces in the path name. Certain functions still don't work properly if you install in C:/Program Files. PTC has been trying to fix this for haow many years?
If you're running a floating license on a server with Flex/LM then that allows you to checkout the license ID to use on another computer. Flex/lm calls this license borrowing. Let say you have a laptop you travel with but use a desktop for Pro/e. Flex/lm will allow you to borrow the license to use Pro/e on the laptop. Yo can find more information about this on Flex/lm's website.