ExMerge allows you to extract data from mailboxes into PST files. You can use it the opposite way too - import data from PST files into mailboxes. Here you can see how this can be done. It is important to point out that ExMerge v.6 which is available for download from MS site should only be run from Exchange Server 2003 or from computers with the Exchange 2003 administrative tools loaded. If you are running Windows 2000 or NT4.0 like in the scenario bellow you have to use ExMerge v.3. You can download it from here.