Exactly, I'm upvoting this to prevent poor souls stuck on Windows from looking for these nice solutions...
Not sure what I'm doing wrong, but I've never has success with non-windows OS's.
(and yes, it's VNC, not RDP, I believe the oracle extension pack actually allows for Virtualbox to do RDP as well. But you can stay GPL-only and still support headless VNC. I believe phpVirtualbox uses it with beautiful results)
Otherwise, don't you have to do everything by hand to configured xrdp on the Linux guest?
Much of the Windows world is still on Windows 7, and it would be rather ironic if they were updating because of concerns about software phoning home...