[Delphi] 用API函数得到操作系统类型

最近一个东西想要升级前判断本级操作系统：
[code]unit Unit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls, CommDlg;
type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
type
TOSVersion = (osUnknown, os95, os95OSR2, os98, os98SE, osNT3, osNT4, os2K, osME, osXP);
var
Form1: TForm1;
implementation
{$R *.DFM}
function GetOS :TOSVersion;
var
OS :TOSVersionInfo;
begin
ZeroMemory(@OS,SizeOf(OS));
OS.dwOSVersionInfoSize:=SizeOf(OS);
GetVersionEx(OS);
Result:=osUnknown;
if OS.dwPlatformId=VER_PLATFORM_WIN32_NT then begin
case OS.dwMajorVersion of
3: Result:=osNT3;
4: Result:=osNT4;
5: Result:=os2K;
end;
if (OS.dwMajorVersion=5) and (OS.dwMinorVersion=1) then
Result:=osXP;
end else begin
if (OS.dwMajorVersion=4) and (OS.dwMinorVersion=0) then begin
Result:=os95;
if (Trim(OS.szCSDVersion)='B') then
Result:=os95OSR2;
end else
if (OS.dwMajorVersion=4) and (OS.dwMinorVersion=10) then begin
Result:=os98;
if (Trim(OS.szCSDVersion)='A') then
Result:=os98SE;
end else
if (OS.dwMajorVersion=4) and (OS.dwMinorVersion=90) then
Result:=osME;
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
os:TosVersion;
osVersion:string;
begin
os:=Getos;
case OS of
os95, os95OSR2: OSVersion:='Windows 95';
os98: OSVersion:='Windows 98';
os98SE: OSVersion:='Windows 98 第二版';
osME: OSVersion:='Windows Millenium Edition';
osNT3, osNT4: OSVersion:='Windows NT';
os2K: OSVersion:='Windows 2000';
osXP: OSVersion:='Windows XP';
end;
showmessage(osversion);
end;
end. [/code]