Some server administrators use virtualization to create a copy of an existing installation of an operating system, plus its data, which they then run virtualized and play with to see if configuration changes or updates will cause any harm. If you manage workstation computers and want to be sure a Windows update is OK before rolling it out, you could do the same thing--just test it in a virtualized machine first.
5. Run Linux on Top of Windows (or vice-versa)
Want to give Linux a try but can't face repartitioning your computer's hard disk? Provided that it would ordinarily install on your computer, you can run just about any operating system inside a virtual machine, including most Linux distros.
Linux and Mac users have been using virtualization for years to run Windows on top of their chosen OS in this way.
If you run a Linux machine for mail or Web services, as examples, having a desktop version of Linux for occasional use will also make it easier to communicate with the server. There's no need to install PuTTY on Windows to communicate via secure shell (SSH), for example, because Linux has that kind of thing built-in.
6. Back Up an Entire Operating System
Because the virtual OS is entirely contained within a series of files, backing it up is as simple as backing up any other files. It's the same with virtualized server installations too. If you're running a virtual machine on a server to host your mail server, and it's brought down by a hack attack, then bringing things back to working order is as simple as restoring the backup files (assuming the vulnerability that allowed the hack is quickly addressed once things are up and running, of course).
Bear in mind that creating a copy of a VM creates legal issues. Backing up should be fine, but if you create a copy of a VM installation to give to a friend, for example, then you'll be contravening copyright laws (assuming they apply, as with Microsoft, but not always with Linux).
7. Create a Personal Cloud Computer
If you're out of the office, there's no need to take your laptop with you. Just leave it running (with power saving turned off!), take your mobile phone or tablet computer instead, and access the laptop via a Remote Desktop Protocol (RDP) connection over the Internet. This will let you access the same desktop environment you're used to, although there'll be no fancy graphics.