You've not said which e-mail client you're using. I'm assuming that it's Outlook Express.
The easiest way to retain your Inbox is as follows:
Go to Start > Search and look for Inbox.dbx
Copy this file to a CD.
Once you've re-formatted your PC and re-installed everything, once again search for Inbox.dbx. This time, right-click on the file and select 'Open containing folder'.
(If the window opens full-size, make it smaller so that you'll be able to fit another window on the screen).
Now insert the CD, double-click 'My Computer' and then double click the icon for the CD. (Once again, ensure that the window is small enough for you to view two windows simultaneously).
Now 'drag & drop' the Inbox.dbx file from the CD folder to the other open window. (When you're asked if you want to replace the existing file, select 'Yes').
To move your address book, search for *.wab and copy the file to a CD. (The file will be something like prawnman.wab, depending upon the name which you're using on your PC). On your new system, open Outlook Express and click on Addresses. Then select File > Import > Address book. Navigate to the CD's wab file and double-click on it.
Chris