Meter el Form1 dentro del Frame1 que hay en el Form2
Código vb:
Ver originalPrivate Declare Function SetParent Lib "user32" (ByVal hWndChild As Long, ByVal hwndNewParent As Long) As Long
Private Sub Command1_Click
SetParent Form1.hWnd, Form2.Frame1.hWnd
End Sub
Saludos