Whether you prefer Linux, Windows, or Mac OS X, you can probably get almost everything you need done with your chosen OS. However, sometimes a task demands an OS that you are not currently using. That's where virtualization programs like Sun Microsystem's VirtualBox 3.0 come in.
What is it? VirtualBox is an open-source virtualization program which lets you run guest operating systems with your native desktop operating system. For instance, if you need Windows to run Quicken, but prefer Linux for all your other work, VirtualBox enables you to bring up Windows and Quicken without leaving your Linux desktop.
What you get is an adjustable window containing the guest operating system floating on the host system. So, for example, you could have a Windows XP guest instance entirely hiding its Linux host system.
There are currently two editions: a full package that is free for personal use (enterprises should contact Sun directly); and the Open Source Edition (OSE), which lacks a few features such as USB support and an easy installer, but comes with complete source code. Both are free.
What does it do? VirtualBox runs on four host operating systems: Windows (through Windows 7), Mac OS X, Linux and OpenSolaris. It can handle a lot more guest operating systems.
VirtualBox itself installs as a standard application in its host operating system. To install a guest operating system, you simply press the "New" icon and follow the wizard's instructions to install the VM (Virtual Machine). You then click the Start button to install your guest operating system on your new VM.
One nice feature is that, besides using the usual CD/DVDs or USB flash drives to install the guest system, you can also use ISO image files on your PC .
I installed VirtualBox 3.0 on three different systems running three different platforms: SimplyMEPIS 8.0, a Debian Linux distribution; Windows XP SP3; and Windows 7 Release Candidate 1. In every case, it installed without a hitch within five minutes.
Once it was in place, I used VirtualBox on MEPIS to run an instance of XP within Linux. I also ran Ubuntu 9.04 within XP and, to try something really out of the ordinary, OpenSolaris 2009.6 within Windows 7. All of these "guest operating systems" ran great using VirtualBox.
What's cool about it? With VirtualBox you can mix and match operating systems depending on your needs. It also gives you an easy way to test out operating systems before deploying them.
Other virtualization programs can let you do that as well, but, in my experience (which goes all the way back to IBM's mainframe virtualization applications) VirtualBox is the easiest to use. Other VM software makes you jump through a variety of hoops to run your guest operating system. VirtualBox makes your guest operating system look and act more like it's simply another application on your desktop.