I could not find a list of Kernel32.dll versions for each release of Windows, but from testing (XP SP3, Vista, Windows 7) the Kernel32.dll version # (Major.Minor) is the same as the Windows version.
What I specifically found (for this version of windows, this version of Kernel32.dll)
* Windows XP (win version 5.1) ,5.1.x
* Windows Vista (win version 6.0), 6.0.x
* Windows 7 (Win version 6.1), 6.1.x
This isn't perfect but it's better than any other method as a double check to see if the installer is reporting the wrong windows version #. (I realize that we should be trying to figure out why the installer reports the wrong version but it's only happening in about 1% of cases and I can't repro it, so a Kludge is called for.)