Microsoft has made their Virtual Server 2005 software available to download for free. Now you can now run your own virtual server on your machine for free! Virtual Server operates on Windows XP Professional, Windows 2003 Server (32 & 64 bit), and Windows Small Business Server. You need to register with Microsoft in order to download the software. To download click here.
"In conjunction with Windows Server 2003, Virtual Server 2005 R2 provides a virtualization platform that runs most major x86 operating systems in a guest environment, and is supported by Microsoft as a host for Windows Server operating systems and Windows Server System applications. Virtual Server 2005 R2’s comprehensive COM API, in combination with the Virtual Hard Drive (VHD) format and support for virtual networking, provide administrators complete scripted control of portable, connected virtual machines and enable easy automation of deployment, and ongoing change and configuration." Via Microsofts Website