If you're using a Windows Mobile Pocket PC or Smartphone, odds are very good that you're using some version of Outlook. The data file for Outlook is a format called PST, which is a surprisingly reliable and robust file, but Outlook isn't the most stable program in the world. You'll want to <A HREF="http://www.pocketpcthoughts.com/articles.php?action=expand,47257">protect that PST file from data loss,</A> unfortunately, Microsoft doesn't make this easy for you.