Here is what I can say with almost certainty
1): Your .pst will definitely work with the newer version of Office / Outlook
2): The email client included in Vista should have a File Import Feature .. it would
be rather inane of Microsoft to not be able to import their own .pst file format. If
that is not an option, then Export the .pst from Outlook in .CSV format and then
see if the Vista Email Client can Import that Format ... one of these methods should work
FYI : From what I have read, the Windows Mail Client in Vista is just a rebranded
slightly changed version of Outlook Express ... Personally, I would stay with Outlook
if you use MS Office or try Thunderbird which is said to be a very good email client