Backup your OE store folder by hand. To find out where it is, use the menu option "Tools / Options", then go to the "Maintenance" tab, and click "Store Folder...", then note the path that is shown. Just copy the entire folder to a safe place either through Windows Explorer or whatever backup program you are using.
 
To restore it after an OS reinstallation, run OE once. Follow the same procedures above to identify the location of the new store folder. Exit OE. Using Windows Explorer, delete the contents of the newly created store folder. Either manually copy the contents of your backed up store folder to the new folder, or restore to that location using your backup utility.
 
Run OE again, and you should find your messages intact.
 
If you want to also back up your address book, you'll have to use "Find Files" on your start menu and look for "*.wab". You'll likely have one that is the actual file, and one that is a backup (it has a "~" in the name). You'll only need the original. Copy it to a safe place. When you've reinstalled the OS and run OE for the first time, search for "*.wab". Replace that one with your backed up copy, and rename the backed up copy to be exactly the same as the one that you are replacing.

the above info is correct.
 
You just need the maintenance folder (and the wab file with your adress book in it )
 
Easiest way to save it is this:
 
just put the storage folder on a different disk
(preferably one you are NOT going to format
 
Every time you reinstall just start up OE, go to the store folder path and change it.
 
and please READ the message that appears, if you chould chose NO there, all your mails will be overwritten by a blank store.
 
This way you never forget to backup your mails, becuase this is in fact easily forgotten.
If your windows chould crash, you always have your mails save.
 
Just don't forget to backup the wab file. I periodically place it in the same storage folder so I always have a copy when I reinstall.

i just drag and drop the e-mail messages to a folder somewhere, it sames them in .eml format.

I have still to try a restore with this but it made a backup quickly and easily.
 
http://www.inachis.com/product_info/
 
look for e-Backup 1.4 section.

On my wifes machine I just did a search for *.dbx files and copyed them to a backup location. Then after a re-install I just told Outlook Express to import from those dbx files at the backup location. If you are using Outlook then you need to do the same but with *.pst files.