Hi, First, a little intro. As part of ongoing work on Boost.Sync we've created quite a few headers with WinAPI declarations that are often needed in Boost libraries. The headers are in boost/detail/winapi and can be used by any library that wishes to avoid including windows.h. The headers declare some symbols that depend on the target Windows version. For example, GetTickCount64 only appeared in Windows Vista. The user can define BOOST_USE_WINAPI_VERSION macro before including any Boost headers to indicate the target WinAPI version Boost should use. If the macro is not defined, the headers attempt to deduce the target Windows version from the _WIN32_WINNT and WINVER macros, if they are defined by the user. Lastly, if everything fails, the headers fall back to a default, which is currently Windows XP. I wanted to ask the community if it is appropriate to raise the default to Windows Vista. The rationale for this is that Vista introduced a lot of useful APIs (in thread synchronization, in particular) and XP is losing its popularity and soon will be completely unsupported by Microsoft. Also, I'm not sure what is the current state of affair, but Microsoft already tried to drop pre-Vista targets in MSVC. Note that I'm not suggesting to drop support for pre-Vista Windows. The user will still be able to enable previous versions of WinAPI in one of the mentioned above ways. Lastly, I'd like to encourage Boost developers to use this protocol for defining WinAPI version used by libraries. It would be ideal if by defining BOOST_USE_WINAPI_VERSION the user would be able to control WinAPI version used by all Boost libraries, not just Boost.Sync and Boost.Chrono (the current users of these headers). If you want to add support for this protocol to your library, simply include boost/detail/winapi/config.hpp. This will result in BOOST_USE_WINAPI_VERSION being defined so that it can be checked by the library. Other headers boost/detail/winapi make use of this macro, you can see them as an example.