Microsoft is offering free downloads of all its supported Windows clients, including Windows 7 RTM, Windows XP and Windows Vista. Starting with the advent of Vista, customers, partners, IT professionals and developers have been able to take advantage of a variety of offerings involving free releases of Windows from the Redmond company. Furthermore, the software giant has made somewhat of a tradition from making sure that XP, Vista and now Windows 7 are available as free downloads in order to streamline various testing, training, planning and adoption programs.

Various releases of Windows, packaged both as ISO and VHD images can be grabbed from the company, and installed into testing environments immediately. In this regard, it is critical to note that one downside of the free Windows OS downloads is the fact that the bits cannot be deployed into production.

On December 29th, 2009, Microsoft has updated the virtual hard disk images of Windows Vista and Windows XP. Initially delivered following the release of Internet Explorer 7, the VPC Hard Disk Images of XP and Vista are designed for testing websites in accordance with multiple Internet Explorer versions. There are three copies of XP SP3 and two of Vista available at no charge via the Microsoft Download Center.

“This download page contains different VPC images, depending on what you want to test. IE6-XPSP3.exe contains a Windows XP SP3 with IE6 VHD file. Expires April 1, 2010. IE7-XPSP3.exe contains a Windows XP SP3 with IE7 VHD file. Expires April 1, 2010. IE8-XPSP3.exe contains a Windows XP SP3 with IE8 VHD file. Expires April 1, 2010. IE7-VIS1.exe+IE7-VIS2.rar+IE7-VIS3.rar contain a Vista Image with IE7 VHD file. Expires 120 days after first run. IE8-VIS1.exe+IE8-VIS2.rar+IE8-VIS3.rar+IE8-VIS4.rar contain a Vista Image with IE8 VHD file. Expires 120 days after first run. For The Vista image, you will need files in that set, downloaded and in the same directory, then run the EXE in the root directory,” Microsoft stated.

In addition to the XP and Vista VHDs, Microsoft is also offering for download a virtual hard disk image of Windows 7. At the same time, Windows 7 RTM Enterprise can also be downloaded as an ISO image and installed on a testing computer. Just as the case for the free Vista and XP copies, the Windows 7 free downloads are also time-bombed offering end users no more than 90 days of free usage.

Users of Windows 7 Professional, Enterprise and Ultimate also have the option to download a free, fully functional, pre-activated copy of Windows XP SP3. They only need to grab Windows XP Mode and Windows Virtual PC from Microsoft. This offering is, however, limited to customers running the Professional, Enterprise and Ultimate editions of Windows 7.

Internet Explorer Application Compatibility VPC Image (free VHDs of XP and Vista) is available for download here.

Microsoft Windows 7 90-Day Eval VHD is available for download here.
Another Windows 7 RTM Enterprise 90-Day Evaluation is available for download here.

Windows XP Mode is available for download here. or here

Windows Virtual PC is available for download here.

Microsoft Virtual PC is available for download x86 or x64.