Microsoft had included the virtual PC with backward compatible of Windows XP to support the users who may had difficult to run their application on Windows 7. This is free and we can see more user will sure include this as part of the Windows 7 installation move forward. Bear in mind, if you have VMware Workstation running on the same machine, you may see the conflict happen if you have your Virtual PC application running and you try to start up a virtual machine from VMware Workstation. There will be a message prompt to inform you that there are existing hypervisor utilize the virtualization capabilities on your machine. The only way to get your VM start up is to end the session of your Virtual PC application. You should able to start your virtual machine up. Not very sure whether there are any workaround beside this, but at this moment, it consider a conflict and we need to choose either 1 to be run at a time.