Why use a virtual machine?

[Steven Vollom]

I have been reading for a couple of hours trying to understand the 
function of a virtual machine, and how to make it work.  I even 
installed VirtualBox, but can't get it working yet.

When you operate using a virtual system, does it function the same as 
using the program, like Win XP?
When operating it, can you make things function, like play a .bin movie 
that won't play in Hardy?
Do you have to purchase a copy of Windows XP to install in the 
VirtualMachine or how do you get it in your computer?  I am not willing 
to pay any more money to Microsoft; I have been abused by them.  
Nonetheless, there are things that I cannot do, because of not having XP 
anymore.

These questions are on the front side of my interest in Virtual Box.  
None are answered in my first two hours of study.  At least they were 
not explained in a way I could understand.  It seems like the answers I 
want are  assumed by the author.  I am even reading about advanced 
benefits and alternative uses, and I still do not know if what I want is 
available.

There are so many ways I am lacking in my understanding of the operation 
of a Linux system, I don't want to waste my study time on a subject that 
doesn't serve a need.  It looks like I could read for days without my 
question being addressed, if ever.

Additionally, if you are required to purchase a copy of XP to install 
into the virtual machine, what is the advantage of that over a dual boot 
system that has XP as an alternate boot?  Before I will ever purchase 
another Microsoft product, I will go without, rather than purchase from 
them.  TIA

Steven