Re: Ubuntu very slow
Ubuntu requires 3D acceleration. If you don't have 3D acceleration (for instance, inside a virtual machine) it uses the CPU to render the desktop. This is quite a bit slower than using your GPU.
Virtualbox comes with a "Guest Additions" package that enables some level of graphics acceleration in Linux guest OSes, you should consider installing that. You may get a bit of a speedup.
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.