If you need to get windows temporary folder for your application you need to follow this steps.

function GetTempDirectory: String;
var
TempDir: array[0..255] of Char;
begin
GetTempPath(255, @TempDir);
Result := StrPas(TempDir);
end;

procedure TForm1.BitBtn1Click(Sender: TObject);
begin
label1.Caption := gettempdirectory;
end;
 Download Source Code