Change the Location of the Outlook Express Mail and News Files (All Windows)
This setting allows you to change the location of the mail and news files stored by Outlook Express to another directory or partition.
Open your registry and find the key below.
Edit the value called ‘Store Root‘ and set it to equal the required path name.
Then move the ‘mail’ and ‘news’ folders from the old location to the new and restart Outlook Express.
Note: The “mail” and “news” folder must be manually created or moved to the new location.