In order to be eligible to receive Windows XP Professional x64 Edition, your computer must have been ordered or built between March 31, 2003 and July 31, 2005 and must contian an x64 processor. You must also have a Retail (Full Packaged Product), System Builder, or OEM version of Microsoft Windows® XP Pro (32-bit) to exchange.

In addition, you must read and agree to the following:
By participating in this program, your 32-bit version of Windows XP Professional will no longer be licensed.
The installation of Windows XP Professional x64 Edition requires you to format your hard drive. You must back up your files and settings prior to the installation or they will be erased. Microsoft is not liable for any loss of data as a result of this installation.
Windows XP Professional x64 Edition requires 64-bit hardware drivers (32-bit drivers are not supported). Drivers for 64-bit Windows are created at the discretion of hardware manufacturers and may not be available for some of your hardware components.
For the purposes of the End User License Agreement for your existing Windows XP Professional (32-bit) software, your installation of this software will be an “Upgrade.”
Customers who are currently supported by a system builder or OEM and choose to upgrade to Windows XP Professional x64 Edition via any means other than their PC manufacturer may void support with their PC manufacturer. We recommend that you check with your PC manufacturer's Web site to find out if they offer or support this exchange.