Ok seems that this never ends... fixed to really work on OS newer than Windows 7. (sorry, I just tested on Win XP and Win 7, I don't have 8, 8.1 or 10 preview).
{ 6.0 vista, 6.1 win 7, 6.2 win 8, 6.3 win 8.1, 10 win 10 }
Win7 := False;
if (Win32MajorVersion = dword(6)) and (Win32MinorVersion >= dword(1)) then // Win7, Win8, Win8.1
Win7 := True;
if (Win32MajorVersion > dword(6)) then // Newer (windows 10)
Win7 := True;
Edit: seems that is the same as doing
Win7 := CheckWin32Version(6,1);