Below is an excerpt from our latest Knowledge base article,
How Does Downgrade Rights for Windows 7 Work?

Windows 7 is the latest offering in desktop operating systems from Microsoft.  In some cases end-users still need to operate with previous versions of O/S such as Windows XP or Vista. As part of Microsoft’s End User License Agreement (EULA), Stealth Computer is an authorized Microsoft OEM and is permitted to offer its customers the ability to run previous versions of XP or Vista Operating Systems.

How does this work? – Downgrade to Microsoft XP as an example.
Windows XP is no longer available for purchase from Microsoft. What you are purchasing is a Windows 7 Pro license with product key, installation media along with a service that allows us (with your permission) to exercise your downgrade rights. You will need to purchase a separate license for each computer ordered.

When choosing the downgrade option Stealth will preinstall Windows XP Pro, 32-Bit, SP3 on your new machine. You will not be provided with Windows XP Pro media.