http://www.microsoft.com/windowsxp/64bi ... grade.mspx
"Welcome! If you have a 64-bit ready PC, you now have the option to receive trial software for Windows XP Professional x64 Edition via CD or download. Read below about the different options for obtaining the pre-release software, and then use the links on the right to register to order the CD Kit or download product files. Please note that in either case, the pre-release software is time-limited and will expire in 360 days."
$20 S&H for CD, d/l free.