取得Windows的SessionID

windows xp的SessionID從0開始
windows vista的SessionID從1開始.0是給特殊權限如SYSTEM

function GetSessionId:DWord;
type _P2S=function (PId:DWORD; var SId:DWORD):BOOL; stdcall;
var P2S: _P2S;
    Hd :HMODULE;
    SId:DWord;
begin
  Result:=0;
  Hd:=LoadLibrary('Kernel32.dll');
  if Hd<>0 then begin
    @P2S:=GetProcAddress(Hd,'ProcessIdToSessionId');
    if Assigned(P2S) and P2S(GetCurrentProcessId,SId) then Result:=SId;
    FreeLibrary(Hd);
  end;
end;