If your VM is really slow check the allocated hardware (especially processor and RAM), under the VM Right click and choose modify,
then go to System.
On the first tab check the amount of allocated RAM:
http://prntscr.com/7nlzj7
On the second TAB increase the amount of CPUs to 2 or more:
http://prntscr.com/7nlzys (Maybe enable PAE/NX)
Under display enable 3D and 2D acceleration and set the memory to maximum:
http://prntscr.com/7nm0ea
That should help to get it faster