저는 델파이 7.0을 쓰고 있는데요...
자료실에 가보면 API에 관한 자료가 있음다..
그거 참고하고 웹에서 찾은 자료임다..
도움이 되었으면 하네요....
이건 제가 테스트해본건데 ... 틀린부분있으면 답변 주세요 ...
그럼...

procedure TForm1.Button3Click(Sender: TObject);
var
  MyVerInfo: TOSVersionInfo;    // holds version information
begin
  {set the size member of the TOSVersionInfo structure}
  MyVerInfo.dwOSVersionInfoSize := SizeOf(TOSVersionInfo);

  {retrieve the operating system version information}
  GetVersionEx(MyVerInfo);
  {display the operating system version information}
  Panel1.Caption := IntToStr(MyVerInfo.dwMajorVersion);
  Panel2.Caption := IntToStr(MyVerInfo.dwMinorVersion);
  Panel3.Caption := IntToStr(MyVerInfo.dwBuildNumber);
  case MyVerInfo.dwPlatformId of
    VER_PLATFORM_WIN32s:        Panel4.Caption := 'Win 32s under Windows 3.1';
    VER_PLATFORM_WIN32_WINDOWS: Panel4.Caption := 'Windows 95';
    VER_PLATFORM_WIN32_NT:      Panel4.Caption := 'Windows NT';
  end;

  {
  Win XP
    -  dwPlatformId = VER_PLATFORM_WIN32_NT and
       dwMajorVersion = 5 and
       dwMinorVersion = 1

  .Net Server
    -  dwPlatformId = VER_PLATFORM_WIN32_NT and
       dwMajorVersion = 5 and
       dwMinorVersion = 2

  win 2000
    -  dwPlatformId = VER_PLATFORM_WIN32_NT and
       dwMajorVersion = 5

  Win Me
    -  dwPlatformId = VER_PLATFORM_WIN32_WINDOWS and
       dwMajorVersion = 4 and
       dwMinorVersion = 90

  Win 98
    -  dwPlatformId = VER_PLATFORM_WIN32_WINDOWS and
       dwMajorVersion = 4 and
       dwMinorVersion = 10

  Win 95
    -  dwPlatformId = VER_PLATFORM_WIN32_WINDOWS and
       dwMinorVersion = 0

  Win NT
    -  dwPlatformId = VER_PLATFORM_WIN32_NT and
       dwMajorVersion <= 4
  }

end;

API 함수중에 GetVersion 이런 게 있답니다.

help 보시면

o distinguish between operating system platforms, use the high order bit and the low order byte, as shown in the following table:

Platform        High order bit        Low order byte (major version number)
Windows NT        zero        3 or 4
Windows 95        1         4
Win32s with Windows 3.1        1        3


For Windows NT and Win32s, the remaining bits in the high order word specify the build number.
For Windows 95 the remaining bits of the high order word are reserved.

이런 설명이 있거든요.

이런 함수는 원하시는 건가요?