How to solve issues with shader model in VirtualBox?

I figured out: To successfully enable shader model, you need to install the experimental WDDM drivers for 3d hardware acceleration. Like described here.

  1. Make sure the device has at least 128MB video memory allocated (256mb recommended).
  2. Safe mode is not required for installing the experimental drivers.
  3. Devices > Install guest additions... (Host + D)
  4. Select: Direct2D-Support (experimental)
  5. It suggests to install the basic 3d driver instead of the WDDM drivers. To install the WDDM drivers, simply click No and Ok.
  6. Finish the installation.
  7. Reboot.

Done.