se la vuoi rotonda tiè...pero secondo me fa schifo!
codice:
Option Explicit

Private Declare Function SetWindowRgn Lib "User32.dll" (ByVal hWnd As Long, ByVal hRgn As Long, ByVal bRedraw As Boolean) As Long
Private Declare Function CreateEllipticRgn Lib "Gdi32.dll" (ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) As Long


Private Sub Form_Load()
    'Imposta la forma della finestra.
    SetWindowRgn Me.hWnd, CreateEllipticRgn(0, 0, 200, 200), True
End Sub