Here are the major applications currently in the desktop virtualization space:
VMware was the first of the desktop virtualization apps, and for many, it remains the best. It is certainly the one product that’s most immediately synonymous in most people’s mind with virtualization, both on the desktop and in server environments.
The most basic version of VMware is VMware Player, which lets you create and run virtual machines on Windows or Linux. Virtual machines created in other versions of VMware, virtual appliances from VMware’s own Appliance Marketplace, and Microsoft VMs and Symantec LiveState Recovery disks, can all be booted and run in Player. Player is free to download and run (although closed-source), and supports both 32- and 64-bit architectures in both guest and host machines.
The more advanced, for-pay Workstation incarnation of VMware adds features like snapshots (capturing the state of a virtual machine’s disk), integration with development environments such as the SpringSource Tools Suite and the Eclipse IDE for C/C++, and Teams (running several VMs together in unison to simulate multiple tiers of a hardware stack.
For most people, Player should more than do the job. For users looking to do formal application development that involves virtualization in some fashion, Workstation is the more appropriate choice.
Sun’s (now Oracle’s) open-source contender to VMware on the desktop—both Workstation and Player–is an impressive product, and not just because it’s free. VirtualBox matches many of the features found in both of those other products, throws in a few of its own for good measure, and is available under licensing that makes it broadly useful to end users and developers alike.
The most common incarnation of VirtualBox, the precompiled binary edition, is free for personal and academic use, and can run on Windows, Linux, Solaris and Mac OS X hosts. Some of the better features of VirtualBox include support for EFI firmware machines, snapshotting (something available in VMware Workstation only, not Player), support for iSCSI targets, CPU hot-plugging, and the ability to dynamically change the amount of memory allocated to a guest while it’s running (“memory ballooning”).
Parallels, Inc. offers their Workstation product for Windows and Linux, and Desktop for the Mac, the latter being one of the main ways (apart from dual-booting) Mac users are able to run Windows software on Apple’s hardware. The feature set of Parallels is close to VMware Workstation; version 4 supports multiple virtual cores, 32- and 64-bit environments in both guest and host, and the ability to not only take snapshots of VMs but clone them and use one as a template for others.
Originally a standalone product for Windows, Microsoft’s Windows
Virtual PC (purchased from Connectix) now exists in two incarnations.
The standalone version, Virtual
PC 2007, is intended for users of Windows XP and Windows Vista. The
new version, Windows Virtual PC, is used with Windows 7 Professional
and Ultimate. It's not a full-blown desktop virtualization product, but
as a way to provide backwards compatibility with 32-bit applications
and device drivers that don’t run correctly in Windows 7 itself. To
that end, Virtual PC is a transitional product, intended mainly to
allow XP users to upgrade to 7 and continue using existing hardware and