uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TmyForm = class(TForm)
    EnumTimes: TMemo;
    Panel1: TPanel;
    Button1: TButton;
    Button2: TButton;
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    fEnumCalled:TDateTime;
    fFindCalled:TDateTime;
    fFindTime:Integer;
  public

  end;

var
  myForm: TmyForm;

implementation
{$R *.dfm}

uses
  DateUtils;

//Careful with definition of this routine (dont forget stdcall)
//otherwise your parameters wont be passed in good order
function OnWindowFound(wnd:HWND; myParam:Integer):Boolean;  stdcall;
var
  sender:TMyForm;
  sWindowName:string;
  nEnumTime:integer;
  processID:DWORD;
begin
    //in this example myParam will contain reference to a TMyForms object
    sender:=TMyForm(myParam);

    //Get the title of this window
    SetLength(sWindowName,255);
    GetWindowText(wnd,Pchar(sWindowName),255);

    //Because in your case most windows are in a different process it is
    //slightly more efficient if you use SendMessage to get the window name
    //SendMessage(wnd,WM_GETTEXT,255,pChar(sWindowName));

    //Calculate the time taken up to here
    nEnumTime:=MillisecondsBetween(Now,myform.fEnumCalled);

    //Add the window and time taken to find it in EnumTimes Memo lines
    sender.EnumTimes.Lines.Add(Format('EnumWindow took %d milliseconds to find '+sWindowName,[nEnumTime]));

    //Continue looking for more windows
    result:=true; //return false if you found what you wanted
end;

procedure TmyForm.Button1Click(Sender: TObject);
var
  nEnumTime:integer;
  lp:Integer;
begin
     //Time of EnumWindows call
     fEnumCalled:=Now();
     EnumWindows(@OnWindowFound,integer(self));
     nEnumTime:=MilliSecondsBetween(Now,self.fEnumCalled);

     //Add the time that enum took to complete in EnumTimes list
     self.EnumTimes.Lines.Add(Format('EnumWindow returned after %d milliseconds',[nEnumTime]));
end;

procedure TmyForm.Button2Click(Sender: TObject);
var
  nFindTime:integer;
  p:PChar;
  sWindowName:string;
  wnd:HWND;
begin
     //Time of FindWindow call
     fFindCalled:=Now();
     wnd:=FindWindow('TMyForm',nil);
     if wnd<>0 then
     begin
       //How long did it take ?
       nFindTime:=MilliSecondsBetween(Now,fFindCalled);

       //Show how long did FindWindow take
       ShowMessage(Format('Find window took %d milliseconds',[nFindTime]));

       //Retreive the window caption. (this time using SendMessage (just another way))
       SetLength(sWindowName,255);
       SendMessage(wnd,WM_GETTEXT,255,integer(p));
     end
     else
       ShowMessage('Could not find any window of class TMyForm');

end;