Hello Peter, Windows mail stores the messages as .EML files. You can use the ImportExportTools extension to import .EML files. It lets you select multiple .EML files at the same time.
Download the ImportExportTools extension by right clicking on the link and choosing Save target as. Now on Thunderbird, go to Tools -> Add-ons (or Extensions) and click Install. Pick the xpi file you downloaded and follow the instructions. Restart Thunderbird This is for Windows Vista Home Premium. You can also check out the following link:
http://forums.mozillazine.org/viewtopic.php?f=28&t=1576435. Hope this helps.
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