Legacy Support in Windows 7

One of the biggest problems Microsoft faces is maintaining compatibility with
older versions of Windows that are still currently being used by a lot of
people. Applications written for these older versions usually do not follow the
best practices required for working on newer versions of Windows and therefore
do not work. This become a major stumbling block for people who wish to move
ahead with their OS for reasons of stability, reliability and security but are
unable to do so due to certain applications that are essential to them and do
not work on the new OS.

In Windows 7, Microsoft heads off in a completely new direction to solve this
problem. Windows 7 has been built to keep the security and reliability
paramount. Applications not written for Windows Vista and above have a low
chance of working with Windows 7. However, to ensure that this does not become a
stumbling block, Microsoft has enabled certain SKUs of Windows 7 to get a
Windows XP license to run in a virtual environment and give users access to
applications installed in this Windows XP directly. This is done using the new
version of Virtual PC now called Windows Virtual PC 7.

Windows Virtual PC 7 (VPC7)

Anyone familiar with virtualization products will know about Virtual PC.
This is a new release of VPC that adds on a number of new features that we will
discuss in this article. It also enables the XP Mode functionality that we
discuss in the next section.

VPC7 is available only for Windows 7 and does not work on Vista or XP. It
also requires hardware virtualization (AMD-V or Intel-VT) on the CPU enabled to
work. A machine bought in the last 3-4 years should most probably have this
feature. You will need to check your machine's BIOS and enable it if it is
there. Once installed, you do not get the familiar Microsoft Virtual PC icon.

The Virtual Machines 'Magic Folder' allows you to create or edit virtual machines.	Set values like RAM and location of the hard disk on the virtual machine.

Instead you get what is known as a “Magic Folder” called Virtual Machines.
You can use this to create and edit virtual machines including things like
changing the name, location, RAM, networking and other settings. Clicking on the
name then starts up the machine in a window just as before.

The virtual machine allows you to run a different OS and use USB devices in them as well.

Once you have installed an operating system in the machine, you should go
ahead and install the “Integration Components” in it. This is the new name for
the older “Virtual Machine Additions”. This not only adds support for mouse and
keyboard capture and release automatically as well as drivers for video and
sound emulation, it now adds the much needed USB support as well. You can now
attach any USB device on your physical machine and have it recognized in the
virtual one as well by selecting it from the USB menu. This means that you can
use USB drives, printers and other devices within the virtual environment as
well.

You also get other features such as auto mounting of all fixed drives on the
system within the VPC and ability to use known folder (Documents, Pictures, etc.
) within apps on the virtual machine. And finally you can go ahead and increase
the resolution of the virtual machine to greater than 1600x1200 since the
display driver has been upgraded to a newer one than the old SiS drivers.

Windows Virtual PC 7 by itself is a great component to add into Windows 7
which allows you to run multiple operating systems and applications together.
However, with the addition of the XP Mode it takes it to a whole new level.

Windows XP Mode (XPM)

This feature is available as a separate download. Basically, this is the
complete Windows XP+SP3 installed inside a virtual hard disk. Once installed,
you get a new Virtual Windows XP icon which you can click to directly open the
preconfigured virtual machine. You can basically do everything you want with
this in VPC7 as with any other operating system.

But where it differs is when you install an application inside the virtual
XP. Once you do finish installing an application and its shortcuts are placed in
the XP's Start Menu, the same shortcuts will suddenly appear in the Windows 7
host system's Start Menu under the Windows Virtual PC | Virtual Windows XP
Applications menu. Install all the apps you want in XP and all of them show up
in Windows 7. Here comes the really cool part. Shutdown the XP virtual machine
and click on any of the shortcuts created in the Windows 7 Start Menu. The
application will suddenly show up with a Windows XP look and feel but running
directly on your Windows 7 desktop.

The advantage of this is that you do not need to run the full Virtual XP
everytime you want to a legacy application. Instead, simply click on the
application's icon in Windows 7 and the app comes up from within the Virtual XP
directly on your Win7 desktop while keeping the XP mode settings. Running legacy
applications cannot be made any easier.

Installing an application inside XPM will also show up the shortcuts in the Win7 Start Menu.	Running WinRAR through XPM and Win7 directly on the same desktop shows you the visual difference between the two.

Internally, Windows 7 uses a set of features from the Remote Desktop
Prototcol 6.1 called Remote Applications and Application Publishing. Both these
technologies work hand-in-hand to run the application inside the virtual
machine, “publish” the UI to the host and simulate the interface of the guest in
the host OS.

XP Mode is a great feature for running those legacy apps till the time they
are upgraded to Windows 7 compatible versions. Along with Windows Virtual PC 7,
this takes away any reason for not upgrading your machines to Windows 7
immediately. You can download the beta releases for both these features from the
Windows 7 site.