Hxcpp will by default look for the Windows/7.1A sdk to remain compatible with windows XP.
You can use the latest SDK by adding the define HXCPP_NO_WINXP_COMPAT, either per-project with "-D HXCPP_NO_WINXP_COMPAT", or globally in your ~/.hxcpp_config.xml file.
See if this helps. If you set the environment variable HXCPP_VERBOSE, you may also get some info on which paths are being used.
Apparently you can target XP directly with VS2013, but I'm not sure how - some magic compile flag somewhere maybe.
Hugh