Windows 7 is already a big punch for Microsoft, according to market share tracker Net Applications, which shows it increasing past all the existing versions of Linux and Windows except Vista and XP and into fourth place hot on the heels of the Mac OS X 10.5.

Except XP Mode does not come automatically, you have to install it. And it does not come with all editions of Windows 7.
Those who have Professional, Ultimate or Enterprise have to download both XP Mode and Virtual machine, on which it runs. Those with Home Premium are fixed. Virtual PC does not come with those editions; Microsoft theoretically does not permit Virtual PC to even run on anything but Vista, XP or the 3 more high editions of Windows 7.

That is not to say Virtual machine does not run there, anyhow, though. And, luckily, the installation process is the same for Virtual machine whether you are licensed for XP Mode or not.
I installed and run it on my laptop running 64-bit Windows 7 Home Premium on an Intel Core 2 Duo with 4GB of memory. Here's how to get going:

Check your Processor
Intel and AMD have both built connects into their processors that permit the host and guest OS to deal off tasks more easily. Virtual machine will work on chips that do not have those clips, but not well. Microsoft gives a free utility to check your processor.

Download Virtual PC
Microsoft must call for a 400 MHz or above Pentium-compatible processor, 35 MB of disk space and Windows XP or Vista. There are 32-bit and 64-bit versions. Virtual machine heeds about the difference. The latest version of Virtual machine supports USB device and is made-up to can support 64-bit OS within the VM also.

Build your VM
After downloading the installation package, run and follow the commands. Then click "Start" and Search for Virtual machine. This will release a wizard that gives. The selection of opening the existing virtual PC, making one with default settings or you will pass through. The process of installing one yourself. Choose last do things like increase memory existing for virtual PC default 128 MB to GB, or increase default virtual hard disk size of 16 GB to something with sufficient space for every OS and applications that you want to work only within the virtual machine. The whole process gets less than time than he set bit Freeware.