Windows8 OS MajorVersion , MinorVersion

mov eax,dword ptr fs:[18h] //! TEB -> TIB

mov ecx,dword ptr ds:[eax+30h] //! self

movzx eax,dword ptr ds:[ecx+0A4h] //! OSMajorVersino 

shl eax,8

or eax,dword ptr ds:[ecx+0A8h] //! OSMinorVersion

  O/S     VERSION dwMajorVersion dwMinorVersion

          Windows 8                          6.2            6                             2

  Windows 7 6.1 6 1

  Windows Server 2008 R2 6.1 6 1

  Windows Server 2008 6.0 6 0

  Windows Vista 6.0 6 0

  Windows Server 2003 R2 5.2 5 2

  Windows Server 2003 5.2 5 2

  Windows XP  5.1 5 1

  Windows 2000 5.0 5 0

  Windows Me  4.90 4 90

  Windows 98  4.10 4 10