Formularios semitransparentes en VB6

Esta api funciona solamente bajo windows 2000 o xp ya que estos sistemas operativos vienen con una capa de directx en forma nativa por lo que si probás en wun win9x no te va a dar bola.
SetWindowTranslucency es la api
Te paso un ejemplo, ma no me puedo extender por que el foro no me lo permite
en un BAS:
Private Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hWnd As Long, ByVal crKey As Long, ByVal bAlpha As Long, ByVal dwFlags As Long) As Long
Private Const LWA_COLORKEY = &H1&
Private Const LWA_ALPHA = &H2&
' Style setting APIs
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Const GWL_EXSTYLE = (-20)
Private Const WS_EX_LAYERED = &H80000
' Win32 APIs to determine OS information.
Private Declare Function GetVersionEx Lib "kernel32" Alias "GetVersionExA" (lpVersionInformation As OSVERSIONINFO) As Long
Private Type OSVERSIONINFO
dwOSVersionInfoSize As Long
dwMajorVersion As Long
dwMinorVersion As Long
dwBuildNumber As Long
dwPlatformId As Long
szCSDVersion As String * 128
End Type
Private Const VER_PLATFORM_WIN32s = 0
Private Const VER_PLATFORM_WIN32_WINDOWS = 1
Private Const VER_PLATFORM_WIN32_NT = 2
' Used to determine parentage.
Private Declare Function GetParent Lib "user32" (ByVal hWnd As Long) As Long
Private Declare Function IsWindowVisible Lib "user32" (ByVal hWnd As Long) As Long
Public Function ClearWindowTranslucency(ByVal hWnd As Long) As Boolean
Dim nStyle As Long
If IsWin2000 Then
' Only work with top-level.
hWnd = GetTopLevel(hWnd)
' Set translucency to fully
' opaque (255).
Call SetLayeredWindowAttributes(hWnd, 0, 255&, LWA_ALPHA)
' Clear exstyle bit.
nStyle = GetWindowLong(hWnd, GWL_EXSTYLE) And Not WS_EX_LAYERED
ClearWindowTranslucency = CBool(SetWindowLong(hWnd, GWL_EXSTYLE, nStyle))
End If
End Function
Public Function SetWindowTranslucency(ByVal hWnd As Long, ByVal Alpha As Byte) As Boolean
Dim nStyle As Long
If IsWin2000 Then
' Only work with top-level.
hWnd = GetTopLevel(hWnd)
' Set exstyle bit.
nStyle = GetWindowLong(hWnd, GWL_EXSTYLE) Or WS_EX_LAYERED
If SetWindowLong(hWnd, GWL_EXSTYLE, nStyle) Then
' Set window translucency to
' requested Alpha value.
SetWindowTranslucency = CBool(SetLayeredWindowAttributes(hWnd, 0, CLng(Alpha), LWA_ALPHA))
End If
End If
End Function
Public Function IsWin2000() As Boolean
Dim os As OSVERSIONINFO
' Layered windows are only available in
' Windows 2000. This function shouldn't
' be called often, so check on demand.
os.dwOSVersionInfoSize = Len(os)
Call GetVersionEx(os)
If os.dwPlatformId = VER_PLATFORM_WIN32_NT Then
IsWin2000 = (os.dwMajorVersion >= 5)
End If
End Function
Private Function GetTopLevel(ByVal hChild As Long) As Long
Dim hWnd As Long
' Read parent chain up to highest visible.
hWnd = hChild
Do While IsWindowVisible(GetParent(hWnd))
hWnd = GetParent(hChild)
hChild = hWnd
Loop
GetTopLevel = hWnd
End Function