Connaitre la durée d'utilisation de Windows

function UpTime: string;
const
ticksperday : integer = 1000 * 60 * 60 * 24;
ticksperhour : integer = 1000 * 60 * 60;
ticksperminute : integer = 1000 * 60;
tickspersecond : integer = 1000;
var
t : longword;
d, h, m, s : integer;

begin
t := GetTickCount;
d := t div ticksperday;
dec(t, d * ticksperday);
h := t div ticksperhour;
dec(t, h * ticksperhour);
m := t div ticksperminute;
dec(t, m * ticksperminute);
s := t div tickspersecond;
Result := 'Uptime: '+IntToStr(d)+ ' Days '+IntToStr(h)+' Hours '+IntToStr(m)+'
Minutes '+IntToStr(s)+' Seconds';
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
label1.Caption:=UpTime;
end;