Free Virtualization Software
One of the biggest obstacles to overcome in setting up a virtualized environment has traditionally been obtaining virtualization software. Thankfully, a variety of free virtualization programs are now available, taking the financial sting out of virtualization.
For Windows 7
If you are running Windows 7 and have hardware virtualization support, download and install Windows Virtual PC (see Figure 7).
Figure 7 Configuring a new virtual machine for use with Windows Vista using Windows Virtual PC
Windows 7, Windows Vista, or Windows XP
Windows 7 users whose systems don't support hardware virtualization can download Virtual PC 2007, which also works with Windows Vista and Windows XP.
Third-party solutions include Sun Microsystems' VirtualBox and VMware's VMware Player, which also work with Linux distributions (distros).
Comparing Virtualization Programs
Microsoft compares Windows Virtual PC and Virtual PC 2007 here.
Labnol's comparison of Windows Virtual PC, Virtual PC 2007, WMware Player 3.0, and VirtualBox 3.0 is available here.