it will take a while depending on the speed of you machine. Be patient.
Once it is up, you can start using just like the computer you are using now!
Note as you shut down your system Reactos will not be permanently on the system. This is only a temporary set up. You will need to use the install CD to have it permanently set up.
Using a virtual machine is a great way to test other operating systems without having to modify your existing set up. (This can also be done on other operating systems, but I did not include that tutorial in this instructable.