// Works only on Windows NT systems (WinNT, Win2000, WinXP)
uses psAPI;
procedure TForm1.Button1Click(Sender: TObject);
var
 pmc: PPROCESS_MEMORY_COUNTERS;
 cb: Integer;
begin
 cb := SizeOf(_PROCESS_MEMORY_COUNTERS);
 GetMem(pmc, cb);
 pmc^.cb := cb;
 if GetProcessMemoryInfo(GetCurrentProcess(), pmc, cb) then
  Label1.Caption := IntToStr(pmc^.WorkingSetSize) + ' Bytes'
 else
  Label1.Caption := 'Unable to retrieve memory usage structure';
 FreeMem(pmc);
end;