I have set up a combined dual boot/Virtualbox system with Windows 8 as my main OS and a Ubuntu 14.04 LTS hard drive which can also be accessed as a virtual machine by VirtualBox using this guide.
Even though I am not a very experienced Linux-, let alone Ubuntu-user, I managed to get it up and running except for one problem:
I would like to use the proprietary fglrx drivers for my ATI Radeon R9 285x when I actually boot into Ubuntu because I expect better performance, and even more for the most trivial reason that the fan of my VGA is running much louder when using the open source driver. But when I choose them, I am no longer able to access my Ubuntu desktop via VirtualBox and get stuck in Login-loop, most likely because it can't load the proper drivers.
On the other hand, I also installed guest additions, which provide me with all the convenience of a full-resolution seamless virtual machine. But when I activate them, they replace the graphics driver also for regular booting of Ubuntu.
So right now I can choose between either a virtual machine with full graphic support but a genuine Ubuntu environment with a loud graphic fan and incomplete graphic support, or a virtual machine with no graphic support at all but a fully functional Ubuntu system. Switching requires re- or deinstalling fglrx each time.
So my question is:
Is it possible to let the system switch between the fglrx driver and the Virtualbox-guest-addition-driver, depending on whether it is booted regularly or in a virtual machine?