If you have an old pst or an old archive pst and you want to view your old email, you can open it in your Outlook profile.
Do not use File, Import and Export menu, especially if it's an Archive pst - you may end up with duplicates and will not be able to remove them using Autoarchive (because archive uses the modified date and importing changes the modified date). Just open it in Outlook.
Open the File, Open, Outlook Data File menu and browse to find the pst you want to open.

This
screen shot is from Outlook 2003. In older versions of Outlook, browse to
File, Open, Personal Folders File.
If you just created your profile and have the Profile dialog open, skip to Step 3 after clicking Finish in the profile wizard.

Select
your new profile from the
Mail dialog and choose Properties, then Email Accounts and finally, View
or change email accounts.Note:
Right click on the top level and choose Close.
Note: You can easily have several pst's in your profile and only need to close it if you prefer to keep the folder list less cluttered or need to move the file.