[john123]

I share some info about Microsoft Outlook .pst file. It provides Outlook Support for your Outlook 2007 version. If you want to access an Outlook 2007 or Outlook 2003 .pst file from a different computer that has an earlier version of Outlook installed, or if you installed Outlook 2007 or Outlook 2003 and have decided to remove it and to use Outlook 2002 or earlier, you must change your .pst file back to an ANSI format. To do so, follow these steps:
1. Start Outlook 2007 or Outlook 2003.
2. On the File menu, click Data File Management, and then click Add.
3. Click Outlook 97-2002 Personal Folders File (PST).
4. Click OK.
5. Name the .pst file, or click OK to accept the default name.
6. Click OK.
7. Click Close.
8. Click Folder List at the bottom of the navigation pane.
9. In the navigation pane, you will now see your new .pst file that you named in step 5.
10. Drag the .pst file information from your existing Outlook 2007 or Outlook 2003 folders to the new .pst file that you created.



source support.microsoft.com