Install this update to remove the prerequisites required to run Windows Virtual PC and XP mode. The prerequisites include a processor which supports hardware assisted virtualization (HAV) which is also enabled in the BIOS. After you install this item, you may have to restart your computer.
Refer links for more details. - Bink.nu | Virtual PC update to remove CPU requirement - Bink.nu Download details: Update for Windows 7 for x64-based Systems (KB977206) Error message about hardware-assisted virtualization for Windows XP Mode in Windows Virtual PC on a computer that is running Windows 7