To open a PST file in Outlook follow these steps:

1. Click on File
2. Navigate to Open & Export and click on Open Outlook Data File

To open a PST file in Outlook 2007 follow these steps:

1. Go to Tools > Account Settings.
2. Navigate to Data Files and click on Add
3. Choose Office Outlook Personal folders File and open a PST file
4. It will appear in the left pane menu.
   

 If you need more information on how to open pst files refer to the following Article.