I replaced a Core 2 Duo E6300 with a Core 2 Quad Q9550 E0 in a Windows 7 machine. XP Mode has stopped working - gives 'cannot start host process...no hardware assisted virtualization' error. Ran securable it reports a big red No for hardware virtualization. Gigabit MB, no BIOS settings related to VT and no MB changes since it worked. Not overclocking. Every spec I can find says Q9550 has hardware support for virtualization. Is this a defective CPU? Intel Core 2 Quad Q9550 Stepping A Revision E0.