Outlook Express creates a .dbx file for each mailbox (Folder). This file stores the emails and related information to access through Outlook Express. The name of this file usually coincides with the name of the mail folder or newsgroup. For example, Inbox.dbx corresponds to your incoming mail folder. For each account, all dbx files are saved in one directory called the store root directory.
All Outlook Express mail folders (.dbx files) are stored in one location called the store folder and all the .dbx files can be found at one place, the Store root/folder directory.
The default location is:
C:\Windows\Application Data\Outlook Express\[GUID]
C:\Documents and Settings\<User>\Local Settings\Application Data\Identities\[GUID]\Microsoft\Outlook Express
[GUID] is the Global Unique IDentifier (technical terminology for a unique long number) used to specify an Identity. Depending on your operating system and upgrade history, your store folder might be located elsewhere. To determine the location of your store folder in Outlook Express, click Tools| Options| Maintenance| Store folder.