Render a scene into a MemDC

Hello,
I am writing OpenGL code in Windows 2000 platform. When I render the scene directly on the window, it works. However, when I first render the scene into a MemDC, then Bitblt the MemDC, the scene won’t show up. ( the PIXELFORMATDESCRIPTOR is set to PFD_DRAW_TO_WINDOW, not PFD_DRAW_TO_BITMAP).
Any hint will be appreciated.