If you find the pst file DS refers to, you will need to make sure that Outlook points to the right place. This is available under Tools > Options > Mail Set Up Tab > Data File Locations button.
For the future so you never get caught by any changes, set the location of your pst file to somewhere else. I have mine on a Data drive so that it is never affected by a change in, to or by the OS. My Data drive is currently a separate physical drive, but it could be just a separate partition. You will need to copy the file to your chosen location using Windwos Explorer (Outlook should not be running when you do this) and then open Outlook and using the menu commands above point at the copy in it's new location.