Const MF_REMOVE = &H1000& Const SC_CLOSE = &HF060
Private Declare Function GetSystemMenu Lib "user32" (ByVal hwnd As Long, ByVal bRevert As Long) As Long
Private Declare Function RemoveMenu Lib "user32" (ByVal hMenu As Long, ByVal nPosition As Long, ByVal wFlags As Long) As Long

' USO delle API (Sostituire a "Me" la form interesata)
Call RemoveMenu( GetSystemMenu(Me.hwnd, 0), SC_CLOSE, MF_REMOVE )



qesto tip funziona con vb6.
purtroppo vb.net non lo conosco