Here are some key points I took from one of the posts, the most important of which is POINT 3.

1. Outlook must be installed on the computer that the .pst file is to be exported.
2. Individual messages from Outlook (.msg) cannot be dragged and dropped into WIndows Mail (or even Outlook Express on XP for that matter)
3. In Outlook on Windows XP export the PST to Outlook Express then import those into Windows Mail
4. Outlook Contacts will need to be exported as a Comma Separated Values text file for import into Windows Contacts

Microsoft, Outlook, PST, Windows Mail, Tips and Tricks, Import PST

Source:? Views on Windows Vista