Автор: http://www.swissdelphicenter.ch

function IconsAreEqual(const Icon1, Icon2: TIcon): Boolean;
 var
   ms1: TMemoryStream;
   ms2: TMemoryStream;
 begin
   Result := False;
   ms1    := TMemoryStream.Create;
   try
     Icon1.SaveToStream(ms1);
     ms2 := TMemoryStream.Create;
     try
       Icon2.SaveToStream(ms2);
       if ms1.Size = ms2.Size then
         // Compare the streams, Streams vergleichen: 
        Result := CompareMem(ms1.Memory, ms2.Memory, ms1.Size)
       finally
         ms2.Free
     end
   finally
     ms1.Free
   end
 end;

 procedure TForm1.Button1Click(Sender: TObject);
 var
   icon1: TIcon;
   icon2: TIcon;
 begin
   icon1 := TIcon.Create;
   icon2 := TIcon.Create;
   try
     icon1.LoadFromFile('c:\Icon1.ico');
     icon2.LoadFromFile('c:\Icon2.ico');
     if IconsAreEqual(icon1, icon2) then
       ShowMessage('Icon 1 and Icon 2 match')
     else
       ShowMessage('Icon 1 and Icon 2 don''t match');
   finally
     icon1.Free;
     icon2.Free;
   end;
 end;