Legacy Support in Windows 7

Apps written for Windows Vista and above have a low chance of working with Win 7. To combat this, Win 7 allows Win XP license to run in a virtual environment

Monday, June 01, 2009

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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.

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