The virtualization support is available in processors that include a virtualization option specific processors with Intel Virtualization Technology (Intel VT) or AMD Virtualization (AMD-V) technology, or virtualization-capable processors from Via.
Suppose you wanted to run other operating systems that are supported for use with Windows Virtual PC from your present Windows OS then this Virtualization is needed.( Note that its not dual/multi booting of OS but you are running another OS from within your present Windows using Virtualization). Or If you are running Windows 7 and want to use Windows XP Mode to access a virtualized instance of Windows XP then also your PC should support Virtualization.
So how to check whether your PC supports it? For this there’s a Hardware-assisted virtualization (HAV) detection tool which checks if the computer processor supports HAV and if this setting is enabled in the BIOS. You can get this tool from the Microsoft Download Center. (HAV Detection Tool 180 KB, User Guide 881 KB)
When you run this tool and if your system does not support virtualization then it shows this result:
and if your system supports Virtualization but is not enabled in the BIOS, then you get this :
If you have a computer that has a HAV capable processor and if this feature is enabled on the processor from the BIOS, then the following screen is shown:
And on such systems you can use Windows Virtual PC or Windows XP Mode on a supported Windows 7 edition
There can be another case as, if you have a machine which has Intel Trusted Execution Technology (Intel TXT) enabled and *if* that setting interferes with the virtualization setting of your processor, then the following screen is shown:
For more details one can refer to the HAV Detection Tool - User Guide available from tool download link.
There are many popular PCs equipped with dual and quad core processors running in your laptops and desktops does not support Virtualization, this I have noticed with many of the Intel range of processors. So even today if you are buying a new laptop , always check whether the processor inside supports Virtualization or not.
You can check this from Intel site : Processor Spec Finder.
Also you can check which of the Intel CPUs support this from http://ark.intel.com/VTList.aspx
If you go to those Intel links given above, one can see even some of the Quad core Intel CPUs doesn’t support virtualization so while choosing your new PC be aware of such facts.
Also check for AMD processors specs here: http://products.amd.com/en-us/
For more details on Windows Virtual PC and Windows XP mode , you can check http://www.microsoft.com/windows/virtual-pc/