if your files are from office 2000, it has no problem reading in office 2007
as for your pst, maybe you can try to clear some of your unwanted mails and compress it. if it is possible then archive it too..
anyway if i am not wrong all .pst can only hold till 2gb..to be able to import/export you will need to know where you .pst sits here
C:\Documents and Settings\YOUR USER ID\Local Settings\Application Data\Microsoft\Outlook