How to make VirtualBox use GPU or fix slow performance problems with ubuntu 12.04 ,12.10,13.04,13.10, 14.10

                                                               step 1

                                  sudo apt-get install linux-headers-$(uname -r)            

                                                               step 2
                    sudo apt-get install build-essential 

step 3

cd /media/

step 4

cd /VBOXADDITIONS_4.3.0_89900/

(in your case  there may be other   numbers)

step 5

then just type 

sudo . /VBoxLinuxAdditions.run

and hit  Enter

step 6

sudo nano /etc/modules

step 7

add       vboxvideo

Ctrl +x  then type y

step 8

/usr/lib/nux/unity_support_test -p

step 9

check if all is ok

REBOOT your pc

UBUNTU 14.10  fri dec5 2014

-----------------------------------------------------------

step 10

If  system still very slow  last chance

step 11

click here 

step 12

choose GNOME CLASSIC (no effects)

the end.

/usr/lib/nux/unity_support_test -p

sudo apt-get install linux-headers-$(uname -r)

sudo apt-get install build-essential

cd /media/VBOXADDITIONS_4.3.0_899660

sudo nano /etc/modules

vboxvideo

reboot your pc