And you don't actually have to set all 5.
If you just set the Unfiled Notes location (down the bottom of the options)
all the others will be default point to that same location. If you want to
set them individually to different locations however you can.
Also, note that if you're trying to share your actual notebook between two
machines you should create the notebook on one machine, and then just open
it on the other machine. You'll have a local cached copy on that other
machine that will stay in sync so you can use it even when it's disconnected
from the first machine.
See this blog post for more details:
http://blogs.msdn.com/chris_pratley/archive/2006/06/07/621692.aspx