uses
  Registry;
 // Read REG_DWORD
procedure TForm1.Button1Click(Sender: TObject);
 var
  Reg: TRegistry;
  RegKey: DWORD;
  Key: string;
 begin
  Reg := TRegistry.Create;
  try
  Reg.RootKey := HKEY_USERS;
  Key := '.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings\URL History';
  if Reg.OpenKeyReadOnly(Key) then
  begin
  if Reg.ValueExists('DaysToKeep') then
  begin
  RegKey := Reg.ReadInteger('DaysToKeep');
  Reg.CloseKey;
  ShowMessage(IntToStr(RegKey));
  end;
  end;
  finally
  Reg.Free
  end;
 end;

 // Write REG_DWORD
procedure TForm1.Button2Click(Sender: TObject);
 var
  Reg: TRegistry;
  Key: string;
 begin
  Reg := TRegistry.Create;
  try
  Reg.RootKey := HKEY_USERS;
  Key := '.DEFAULT\Software\Microsoft\Windows\CurrentVersion\Internet Settings\URL History';
  if Reg.OpenKey(Key, True) then
  begin
  Reg.WriteInteger('DaysToKeep', 20);
  Reg.CloseKey;
  end;
  finally
  Reg.Free
  end;
 end;