Each Notebook should correspond to a folder on a local hard drive, shared
hard drive or SharePoint Library.
Hover the mouse above each Notebook on the lefthand side of the screen and
write down the locations for each one. Unless they are stored on the
network, they will each likely be found as a subfolder under "My Notebooks"
under the current user's My Documents part of their Windows profile.
If the Notebooks are local, copy/move them to the new computer into the
same directory. If the Notebooks are on a network server, you don't need
to move them.
To open them again on the new computer, use File | Open Notebook and
navigate to each folder to open it. Repeat for all Notebooks.