The developer of Robolinux offers a Debian-based GNU/Linux operating system designed to let you run Windows XP or Windows 7 in a virtual machine.
But the latest version of Robolinux goes a step further: It includes a tool that lets you create a virtual machine by cloning your Windows C: Drive, which means it takes just minutes to create a version of Windows that you can run in virtualization in Linux, and it will already have all of your existing programs and data.