Executive Summary: Virtualization is a fast-growing market, and the good news is that you can build your virtual machines (VMs) and manage your environment with free software. See how VMware and Microsoft products stack up against lesser-known virtualization products such as VirtualBox, QEMO, and Oracle VM.

You like free software, right? Virtualization is one of the fastest growing technologies, and one of the key driving factors behind its growth is the fact that many of today’s premier virtualization products are free. This lets organizations use virtualization for many different scenarios without spending a lot of money. Let’s look at the 10 best free virtualization products that work with Windows.

10. VMware Player—VMware Player doesn’t let you create new virtual machines (VMs). However, it runs on both Linux and Windows hosts, and can run both VMware and Microsoft VM images. VMware Player is also the basis for VMware’s thriving Virtual Appliance Marketplace. You can download VMware Player from www.vmware.com/download/player.

9. Xen—Xen is an open-source, hypervisor-based virtualization product. You load Xen from a Linux host, and the latest releases support both Windows and Linux guests. Xen-enabled Linux systems can also run under Microsoft’s Hyper-V virtualization, taking full advantage of the new high performance VMBus architecture. You can download Xen from www.xen.org/download.

8. VirtualBox—VirtualBox runs on Windows, Linux, and Macintosh hosts, and can run Windows Vista, Windows XP, Windows 2000, Windows NT, and many Linux versions as guests. VirtualBox comes in both a commercial and a free version. VirtualBox VMs provide audio, USB, and iSCSI support. You can find VirtualBox at www.virtualbox.org.

7. QEMU—A bit different from the other virtualization products listed, QEMU is a processor emulator. QEMU isn’t an open-source project, but it is free software and is utilized by a number of other products, including VirtualBox and Win4Lin. Its system-emulation mode provides basic support for Windows guests as well as DOS, Linux, and BSD. QEMU is found at fabrice.bellard.free.fr/qemu/about.html.

6. Oracle VM—Not to be left out of the burgeoning virtualization market, Oracle began providing a free Xen variant in late 2007. You manage Oracle VM with a browser-based management console. Although the Oracle VM software is free, Oracle charges for support. You can download Oracle VM at www.oracle.com/technologies/virtualization/index.html.

5. Virtual Iron Single Server Edition—Best known for its virtual infrastructure management capabilities, Virtual Iron also offers Single Server Edition, a free, limited-feature version of its enterprise-class virtualization product. The free version can run no more than 12 VMs and supports a maximum Microsoft Virtual Hard Disk (VHD) import or export size of 18GB. You can get the Virtual Iron Single Server Edition from www.virtualiron.com/products.

4. Microsoft Virtual PC 2007—Virtual PC 2007 is Microsoft’s desktop virtualization product. It has host and guest support for Windows Vista. It also supports multiple monitors, x64 host hardware, and hardware-assisted virtualization. You can download Virtual PC 2007 from www.microsoft.com/windows/downloads/virtualpc.

3. Microsoft Virtual Server 2005 R2—Microsoft’s primary virtualization offering for Windows Server 2003 hosts, Virtual Server 2005 R2 is designed for production server virtualization tasks. It provides 64-bit host support but no support for 64-bit guests. Virtual Server 2005 R2 supports Windows Server guests as well as the popular enterprise Linux OSs. You can download Virtual Server 2005 R2 from www.microsoft.com/downloads/details.aspx?FamilyID=6dba2278-b022-4f56-af96-7b95975db13b.

2. VMware Server—VMware Server runs on both Windows and Linux, and it provides 32-bit and 64-bit support for hosts and guests. VMware Server 2.0, currently in beta, also has experimental support for Windows Vista and Windows Server 2008. Its VM’s have audio and USB guest support as well as support for snapshots. You can get VMware Server at www.vmware.com/download/server.

1. Microsoft Hyper-V Server—Hyper-V Server, as a standalone, costs $29. However, it’s bundled with certain editions of Windows Server 2008, making it essentially free for Server 2008 customers. Hyper-V uses modern hypervisor-based architecture. It requires an x64 processor with hardware-assisted virtualization, and can run Windows and Linux guests. You can download the Hyper-V beta as part of Server 2008 RC1 at www.microsoft.com.nsatc.net/downloads/details.aspx?familyid=8F22F69E-D1AF-49F0-8236-2B742B354919.