After the helpful advice I received in this mailing list and other forums, I'm happy to report that the three Boost libraries, filesystem, regex, and asio have been successfully ported to Windows Phone 8.1. Our corporate product is back up and running on Windows Phone 8.1 devices. I assume there are others who will be happy to download the new Boost code for use in their WP 8.1 apps. These libraries will hopefully join those already ported by Steven Gates of Microsoft [http://blogs.msdn.com/b/vcblog/archive/2014/07/18/using-boost-libraries-in-w...]. I am therefore beginning the process of verifying the port using the Boost regression test suite (I have to decide how to get them to run under Windows Phone 8.1). When the code has passed the regression suite I will issue a pull request against the GitHub repository. Thanks again to everyone in this list for their helpful comments and suggestions, Moshe Rubin Technology Manager Hyperlync Technologies Ltd. Jerusalem, Israel