I use this type of virtualization when writing my computing books: I keep a word processor open in my everyday operating system, and use a virtualized operating system installation as a testbed. Most good virtualization software allows ‘snapshots' to be taken of the OS, so if I make a mess, I can ‘rollback' to a previous snapshot when everything was sweet.

Mac and Linux users are able to virtualize Windows in this way, so they can run Windows-only software.

Running virtual operating systems on top of another operating system is known as Type 2 (hosted) virtualization. Free-of-charge examples include VMware Player and .

Companies like VMware also produce Type 1 (bare metal) virtualization software. This doesn't need to run on an operating system. It's effectively a simple operating system in itself that does nothing more than host virtualized OSes. Type 1 virtualization is found on servers. Examples include the open source Xen software, and VMware's ESX products.

Virtualization is spreading beyond servers and desktop computers, , where a user can have a "work" OS alongside a "home" OS, and can flip between them as need be. This allows IT managers to ensure that any work data is secure. The same type of virtualization is almost sure to spread to tablet computers too, for the same reasons; users will be able to have home and work states on the same hardware, with work data protected in its own virtual machine.