VirtualBox is a virtualization solution used to launch operating systems inside virtual machines without a need to install it to real hardware. VirtualBox creates a separate file with hard drive image where operating system can be installed. This image is used by a virtual machine which is actually just one more window in your system but has a full-functional OS inside.
VirtualBox is convenient when it is necessary to often switch between different OSes (for example, when testing behavior of some application in different distributions). One should note that virtualization consumes significant resources, and you need sufficient RAM to launch virtual machines without significant performance drop.
In order to install VirtualBox in Windows(TM), one should go to VirtualBox.org official site and choose a version of the product suitable for your OS version and hardware platform. You will be provided with a wizard which will help to install VirtualBox on your machine.
1. After installation, launch the VirtualBox application. In order to install ROSA, you will need to create a virtual machine first. This can be done using the "Machine" - "New..." menu entry. VirtualBox will provide you with a step-by-step wizard with a lot of hints. The wizard is very intuitive, so we will not describe it here. After the machine is created, it will be displayed in the list of machines at the left side of the VirtualBox window.
2. The next step is to setup system settings. Select your machine and then click "Settings...". Go to the "System" section. Here you should set the settings suitable for you purposes. If in doubt, you can read hints displayed at the bottow of the window.
Note that if you are going to install the 32-bit ROSA in VirtualBox, make sure you have PAE enabled in the settings of the virtual machine (see "System" - "Processor" - "Enable PAE/NX").
3. Now go to the "Storage" section in the Settings window. Select "IDE Controller", click on the CD image, press "Choose disk" and choose ROSA ISO-image. Press "ОК" and return to the main window. Now you can press "Start" to launch your virtual machine. The machine will boot from ISO image and ROSA installation will begin.
So now you can select your virtual machine and press "Start" in the top part of the VirtualBox window. Since we are installing ROSA to a virtual machine, it is safe to leave default values for most of parameters asked during installation.