Windows Virtual PC  (WVPC) is seamlessly integrated into the Windows 7 desktop and among many new features offers one called Virtual Applications.  You can work in full desktop mode with the new WPVC, but the Virtual Applications feature enables applications that run in the Virtual Machine to present themselves seemlessly in the Windows 7 taskbar and desktop experience. 

 

Windows Virtual PC (WVPC) and Windows XP Mode for Windows 7 are currently in Release Candidate.  Please check out the WVPC Engineering blog here: http://blogs.technet.com/windows_vpc/