first of all, try posting questions in the correct category ;) .
secondly, it depends on what e-mail application you are using, and how it has been setup.
most e-mail programs will have an option generally under the file menu called export, this should export your settings and e-mails to a file, which you can put onto another drive/cd/floppy and then copy back once your done.
if you know the program your using for e-mails it would help in answering the question a little more clearly ;)