Personal Storage File (.pst) is the file format for the data saved in Microsoft Outlook and Outlook Express. These files sit on the computer and can be shared between both programs. To create a separate Outlook Express .pst file, you will need to back up or export your files into a .pst file in a location other than the main Outlook Express folder.
Open Outlook Express and click on "Tools > Accounts."
Click on a mail account to select it and then click on "Export."
Select the location of the folder you want to save the .pst file to in the "Save In" box. Click on "Save." Outlook Express will save all of your e-mail files into a .pst file and store them in the folder that you chose.
Click "Close" to close out of the forms and go back to the main Outlook Express window.