Well since neither of these people seem to be helping you in any way let me tell you the way that I do it. This is the only way that I know of to back outlook express mail/mail folders up when reformatting.
First if you right click on the inbox (or any of the folders in outlook) you will see a listing of where the data is stored the string should look something like this:
C:\WINDOWS\Application Data\Identities\{13B0E865-3D2B-4E30-8012-62E1B35FA404}\Microsoft\Outlook Express\Inbox.dbx
Once you find where the data is at, I take the Outlook Express folder and copy it to another drive or cdrw or whatever you use to back up. When you get all setup again on your new install you can copy and paste this right back into there. If you open this up to the MICROSOFT folder and paste it there it will ask if you want to write over the existing folders and answer yes to all. This will put Outlook express right back to where it was you won't miss a beat
Alright to help you further you can go to tools then accounts then export and this will export your mail server info so that you won't have to bother setting it up on the new install just import it after installation and you will be in business.
Hope this helps you out

LMK