"The hardware-accelerated OpenGL support is deemed experimental
in VirtualBox 2.1. OpenGL support is only exposed to Windows XP and
Windows Vista 32-bit guests at this time, but support for other
platforms is expected in the future. Additionally, Sun Microsystems
also has plans for supporting DirectX acceleration of guest
operating systems in a future release. All the guest OS needs to do
is install an OpenGL driver for what is recognized as a virtual
hardware device that in turn communicates with the host's GPU."