I googled around and found a solution in microsoft.com. Here it is just in case any of you find yourself in my position :
SUMMARY
This article describes how to back up and restore your messages, Address Book, mail accounts, and news accounts in Outlook Express 5 and later. If multiple Identities are in use for Outlook Express, these steps should be repeated for each Identity and the backup data segregated accordingly. This will facilitate restoration of each Identity.
MORE INFORMATION
To backup Outlook Express data: • Copy mail files to a backup folder
• Export the Address Book to a file
• Export the mail account to a file
• Export the news account to a file
To restore or import Outlook Express data: • Import messages from the backup folder
• Import the Address Book file
• Import the mail account file
• Import the news account file
Copy Mail Files to a Backup Folder
To make a backup copy of your Outlook Express e-mail message files: 1. On the Tools menu, click Options.
2. On the Maintenance tab, click Store Folder.
3. Select the folder location, and then press CTRL+C to copy the location.
4. Click Cancel, and then click Cancel again to close the dialog box.
5. Click Start, and then click Run.
6. In the Open box, press CTRL+V, and then click OK.
7. On the Edit menu, click Select All.
8. On the Edit menu, click Copy, and then close the window.
9. Right-click any empty space on your desktop, click New, and then click Folder.
10. Type mail backup for the folder name, and then press ENTER.
11. Double-click the Mail Backup folder to open it.
12. On the Edit menu, click Paste.
13. Close the Mail Backup window.
Export the Address Book to a File
NOTE: This step is very important when multiple Identities are in use. A .WAB (Windows Address Book) file is used by Outlook Express 5.x and 6.0 versions, even if multiple Identities are used. The individual data for each Identity is stored in a folder, by user name, within the .WAB file in use.
Exporting this data, while logged in to a specific Identity, is the only means of segregating the Address Book data. If the .WAB file becomes dissociated from the user Identities, the data can only be exported in total - not folder by folder.
Another reason to export the .WAB file to a .csv file is that if the .WAB file is shared with Microsoft Outlook, the addresses are stored in the *.pst file in Outlook. When you export the file from the Outlook Express File menu to a *.csv file it exports the correct contacts. If the Address Book is shared with Microsoft Outlook, you are not able to export from within the Address Book on the File menu. This option is dimmed or not available.
To export your Outlook Express address book: 1. On the File menu, click Export, and then click Address Book.
2. Click Text File (Comma Separated Values), and then click Export.
3. Click Browse.
4. Locate the Mail Backup folder that you created.
5. In the File Name box, type address book backup, and then click Save.
6. Click Next.
7. Click to select the check boxes for the fields that you want to export, and then click Finish.
8. Click OK and then click Close.
Export the Mail Account to a File
To make a backup copy of your Outlook Express mail account: 1. On the Tools menu, click Accounts.
2. On the Mail tab, click the mail account that you want to export, and then click Export.
3. In the Save In box, locate the Mail Backup folder on your desktop, and then click Save.
4. Repeat these steps for each mail account that you want to export.
5. Click Close.
Export the Newsgroup Account to a File
To make a backup copy of your Outlook Express news accounts: 1. On the Tools menu, click Accounts.
2. On the News tab, click the news account that you want to export, and then click Export.
3. In the Save In box, use locate the Mail Backup folder on your desktop, and then click Save.
4. Repeat these steps for each news account that you want to export.
5. Click Close.
Importing Outlook Express data
To restore data, you may need to re-create the Identities for each user, prior to using the following steps. Repeat each step, as needed, for each Identity.
Import Messages from the Backup Folder
To import your Outlook Express e-mail messages from the Backup folder: 1. On the File menu, point to Import, and then click Messages.
2. In the Select an e-mail program to import from box, click Microsoft Outlook Express 5 or Microsoft Outlook Express 6, and then click Next.
3. Click Import mail from an OE5 store directory or Import mail from an OE6 store directory, and then click OK.
4. Click Browse, and then click on the Mail Backup folder on your desktop.
5. Click OK, and then click Next.
6. Click All folders, click Next, and then click Finish.
Import the Address Book File
To import your Outlook Express address book: 1. On the File menu, click Import, and then click Other Address Book.
2. Click Text File (Comma Separated Values), and then click Import.
3. Click Browse.
4. Locate the Mail Backup folder on your desktop, click the address book Backup.csv file, and then click Open.
5. Click Next, and then click Finish.
6. Click OK, and then click Close.
Import the Mail Account File
To import your Outlook Express mail account file: 1. On the Tools menu, click Accounts.
2. On the Mail tab, click Import.
3. In the Look In box, locate the Mail Backup folder on your desktop.
4. Click the mail account that you want to import, and then click Open.
5. Repeat these steps for each mail account that you want to import.
6. Click Close.
Import the Newsgroup Account File
To import your Outlook Express news account file: 1. On the Tools menu, click Accounts.
2. On the News tab, click Import.
3. In the Look In box, locate the Mail Backup folder on your desktop.
4. Click the news account that you want to import, and then click Open.
5. Repeat these steps for each news account that you want to import.
6. Click Close.