This article will help describe how to manage PST files.
4. Browse to the PST file that you want to add to Outlook and click Open.
The file name that you specify for an Outlook Data File (.pst) appears in the Navigation Pane. The default display name for Outlook Data Files (.pst) is Personal Folders. This can be confusing if you work with multiple Outlook Data Files (.pst) that were created in previous versions of Outlook. We recommend that you use a descriptive display name for each Outlook Data File (.pst).
NOTE: Changing the display name does not rename the file. Only the name as it appears in the Navigation Pane is changed.
When you no longer need frequent access to an Outlook Data File (.pst), you can close the file. A closed file no longer appears in the Navigation Pane, but is not deleted from your computer.
NOTE: If the Close command is not available, you are probably trying to remove the default Outlook Data File (.pst) file that is used to save your new messages. If you were to remove that data file, new messages would have nowhere to go.