简单的部分透明比较难做，不过可以换个方式考虑一下。
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把本问题转换成在VB.NET 2005环境下创建不规则窗体（＝普通窗体 － 透明部分）问题，解决方法就很多了，网上也有许多例子。如 章立民 的书里就详细讲过。
大致思路如下：
1。将backgroundimage设成一个位图（点阵图）
2.将Transparaencykey设成位图的背景颜色（位图最取背景单纯，单纯部分将成为透明部分）
3.如需要可以将formborderstyle设为none，会移除标题栏，并需要手动编写窗体移动、关闭等动作代码，
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hwnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long
Private Const gwl_exstyle = -20
Private Const lwa_alpha As Long = H2
Private Const ws_ex_layered As Long = H8000
Private Sub Form_Load()
Dim Fattri As Long
Call SetWindowLong(Me.hwnd, gwl_exstyle, Fattri Or ws_ex_layered)
Call SetLayeredWindowAttributes(Me.hwnd, 0, 200, lwa_alpha)
End Sub
你不用反复问这个问题了，VB很难实现的。要么窗体整体半透明（用LWA_ALPHA常数指定透明度），要么就窗体完全透明，控件不透明（用LWA_COLORKEY常数指定透明色）。不过你可以把两种窗体结合使用，就是用一个半透明的窗体做背景，上面覆盖一个同样大小的完全透明（控件不透明）的窗体，曲线实现你的目的。
下面代码能能使窗体透明，但控件不透明：
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 Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hwnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long
Private Const WS_EX_LAYERED = H80000
Private Const GWL_EXSTYLE = (-20)
Private Const WS_EX_TRANSPARENT = H20
Private Const LWA_ALPHA = H2
Private Const LWA_COLORKEY = H1
Private Sub Form_Load()
Dim rtn As Long, ctrol As Control
rtn = GetWindowLong(hwnd, GWL_EXSTYLE)
rtn = rtn Or WS_EX_TRANSPARENT
SetWindowLong hwnd, GWL_EXSTYLE, rtn
Me.Show
DoEvents
For Each ctrol In Me.Controls
ctrol.Refresh
Next
'SetLayeredWindowAttributes hwnd, 0, 100, LWA_ALPHA '100值可调，0-255之间，越小透明度越高
'SetLayeredWindowAttributes hwnd, RGB(0, 0, 0), 0, LWA_COLORKEY '将窗体上的黑颜色去掉
End Sub
Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Const WS_EX_LAYERED = H80000
Private Const GWL_EXSTYLE = (-20)
Private Const LWA_ALPHA = H2
Private Const LWA_COLORKEY = H1
Private Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hwnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long
Private Sub SetFormTranslucency(hwnd As Long, crKey As Long, bAlpha As Byte, dwFlags As Long)'实现半透明窗体
Dim rtn As Long
rtn = GetWindowLong(hwnd, GWL_EXSTYLE)
rtn = rtn Or WS_EX_LAYERED
SetWindowLong hwnd, GWL_EXSTYLE, rtn
SetLayeredWindowAttributes hwnd, crKey, bAlpha, dwFlags
End Sub
Private Sub Form_Load()
Call SetFormTranslucency(Me.hwnd, 0, 200, 2) '窗体半透明，200为透明值
End Sub
可以实现窗体和窗体上的控件全都半透明，透明度可调
添加一个公共模块 添加如下代码
Public Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Public Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hwnd As Long, ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long
Public Const WS_EX_LAYERED = H80000
Public Const GWL_EXSTYLE = (-20)
Public Const LWA_ALPHA = H1
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再在每一个窗体的代码上添加如下代码
注意，窗体上有三个控件，text1，command1，label1，这些都是半透明的
Private Sub Form_Load()
Me.BackColor = vbWhite
Text1.BackColor = vbWhite
Command1.BackColor = vbWhite
Label1.BackColor = vbWhite
Dim rtn As Long
rtn = GetWindowLong(hwnd, GWL_EXSTYLE)
rtn = rtn Or WS_EX_LAYERED
SetWindowLong hwnd, GWL_EXSTYLE, rtn
SetLayeredWindowAttributes hwnd, vbWhite, 150, 2 '最后一个参数为 1 时， 是 挖去 第二个参数指定的色，第3个设置透明度的参数无效， 最后一个参数为 2时，第2个参数无效，第3个参数有效 设置透明度范围 【0，255】
End Sub
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我没用过vista，不知是否是同一个效果
