Use Citrix Receiver and Dazzle running on Windows 7 to access two different Virtual Desktops through Citrix XenDesktop. The two Virtual Machines are running Windows Vista and Windows 7.
The Vista VM is running on VMware vSphere the Windows 7 VM is running on Microsoft Hyper-V 2.0.
VMware ThinApp Application Virtualization is used to run Office 2007 and 2010 from both Vista and Windows 7 Virtual Desktops. At the end VMware ThinApp 2010 executes Office 2010 from a local Windows 7 instance.