But you'd expect XP Mode to require something extra from the hardware, and here is where the company's playing things low-key. Windows Virtual PC requires a computer with 2 GB of DRAM and 20 GB of free storage space for the creation of a virtual hard disk. The XP Mode drop-in consumes 2 GB on its own, plus another 15 GB for virtual storage. Experience with WVPC's predecessor, Virtual PC 2007, tells me you really need 4 GB of DRAM at least, and 50 GB of total free space. On the one hand, that's probably too much for your "old PC," but you don't want to run Windows 7 on an old PC anyway -- not so it can run Windows XP on the side. The users who will take advantage of XP Mode will be those who require the convenience and efficiency of having both modes of operation in a single machine.
The other big requirement -- one which Virtual PC 2007 did not have -- was for hardware-based virtualization support through the CPU. If you're judging from CPU model numbers alone, you could get confused by this; but typical consumers don't make such judgments based on model numbers anyway. They look for logos such as the Intel vPro and AMD-V symbols, which certify a machine as supporting virtualization in hardware.
For AMD-based machines, practically all Opteron server CPUs support AMD-V, as do all Phenom desktop processors, all Athlon 64 X2 processors with Socket AM2 dating back to 2007, and all dual-core Turion 64 X2 processors. For Intel desktop CPUs, all dual-core Core 2 Duo E6xxx (65 nm), E7xxx, and E8xxx series, as well as Extreme branded CPUs support Intel VT, and all Core 2 Quads including Extreme support it as well. In mobile, the picture is a little spottier: Only some of the first mobile Core 2 Duo T5xxx series support VT; but in the 45 nm generation, all of the Core 2 Duo U-series, the T9xxx, the P, SP, SL, and SU series support VT. All Extreme branded mobile CPUs support VT, as well as all mobile Core 2 Quads.
