VMs (Virtual Machines) can be very helpful tools for redundancy, backup, testing, and running a very clean environment. The nice thing about a VM is that if one goes bad, or starts acting up, you just grab a recent snapshot and it's like the infection or breakage never happened. Actually, it's not like it never happened. For that clone, it didn't.

Clones are a great way to backup or copy working environments. This is less productive with commercial software that constantly checks to see if its license is in violation and much less useful if your hardware requirements constantly change.

Most people use Virtual Machines for some form of testing. The VM environment allows you to run multiple copies of the same Operating System and various software so you can tweak performance or test new software. However, for the production environment these same tools can come in quite handy.

The one space where a real OS (Operating System) will out perform a VM is aggressive desktop workstations with complex or changing hardware. This is where the driver and interface issues come into play. Most firewire, USB, etc. devices work through standardized interfaces and the OS itself handles the behavior internally. However, if PCI cards were to change, the hardware drivers available in the base VM software may not be able to interpret them to the OS. And, some operating systems (like Windows) have certain hardware where the drivers are very complex and written directly to the hardware. A VM can get in the way of performance. Intense graphics cards is a good example, and graphic design is a possible work environment where VMs won't work.

Images are a great way to create a similar advantage to VMs without the hassles of driver compatibility. With an image, you simply image the perfect working machine and store a copy of that image somewhere. With responsible data storage and backup practices you can replace your questionable computing environment (OS, software, updates, and fear of virus) in less than an hour in most cases. You simply build the dream environment, run all the updates, image the system, and place it aside for a possible reinstallation.
To avoid the possibility of corruption or infections, never image a running system that has been exposed to the known risks or drudgery of daily workload. Build the new image, run all the updates, install all the new software, and image it for a more up to date image. A relatively recent image will cut the reinstallation process to a tiny fraction. On a faster machine you can cut reinstallation from hours to minutes.

There are various Virtual Machine developers, some commercial and others free and open source.

• http://www.vmware.com/ VMware is a commercial and enterprise VM developer. They offer Virtual Machine software for Mac, Linux, Windows, and bare metal management. VMware runs on Linux, Windows and Mac environments and can host Windows, Linux and FreeBSD (see website for other OS guests). The Mac version only hosts Windows.
• http://www.parallels.com/ Parallels is a commercial VM developer. They offer Virtual Machine software for Mac, Linux, and Windows. The environment can host Windows, Linux and FreeBSD in the Windows or Linux host. The Mac version only hosts Windows.
• http://www.virtualbox.org/ Virtual Box is a free and open source Virtual Machine project developing VM environments for Linux.Windows, Linux, Macintosh and OpenSolaris. The VM environment can guest many versions of Windows, Linux, Unices, and BSDs.
• http://www.microsoft.com/windows/virtual-pc/ Microsoft is in the game with virtualization for Windows PCs.