If you are talking about Outlook XP (not Express) you will find it clicking in Outlook on file -> data folder (or something like that) -> Open the working folder (or something like that). Browsing to that folder will be slightly tough, since it's located in some hidden folders.
I don't know how to import the outlook.pst to apples mail.app anymore, but I did succeed (2002
). I was googling for this and found a step by step instruction. Unfortunately I didn't save it and don't remember the site, but once I find it again, I will come back to this thread and post it..