Out of those four programs it's really only Parallels Desktop and VMWare Fusion that we'd recommend for most Mac users. You do have to pay for them - as well as paying for a copy of Windows too - but they work very well and give beginners plenty of help to get started. Parallels Desktop perhaps has a slicker interface, but the two programs work in basically the same way and offer the same core set of features.
When you launch Parallels or Fusion for the first time they both present you with a 'wizard' - a control panel that provides a step-by-step guide to creating a virtual machine on your Mac. The main option for most people simply will be to create a virtual machine that runs Microsoft Windows. Both programs allow you to insert a Windows installation DVD, or to use an 'image file' that you can download from the Microsoft web site. They've both been updated to work with Windows 10, and will go back as far as Windows XP and even the pre-Windows MS-DOS operating system too.
If you're already using Boot Camp to run Windows on your Mac then both Parallels and Fusion will also allow you to quickly convert your existing Boot Camp partition into a virtual machine.
Running Linux and other operating systems in Parallels Desktop or VMWare Fusion
Windows isn't the only option for creating virtual machines, either. For Linux fans, Parallels and Fusion both allow you to create virtual machines that run various versions of Linux. You can even create a virtual machine that runs OS X itself - which can be really handy for trying out things like the beta version of El Capitan, or for developers who want to test their software on a safe virtual machine that won't affect any of their important work files. There are a couple of differences here, though.
For some users, the choice of operating systems that you can use on your virtual machines may make the difference between buying either Parallels or Fusion. Parallels Desktop can create virtual machines using Android and ChromeOS, which will be really useful for developers of mobile apps, while Fusion sticks to its corporate computing roots by supporting the old Netware operating system that was used by many large organisations in the past.
Full-Screen Windows with Parallels Desktop or VMWare Fusion
When Parallels and Fusion were first developed they would display the Windows desktop within its own window on your Mac desktop. Any Windows apps that you wanted to run on your virtual machine would then appear in their own window-within-a-window, which could be a bit of a wrench for your brain at times. So, over the years, both programs have developed ways of more smoothly integrating Windows apps into the Mac environment.
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