IF you qualify, you can land a free copy of WinXP 64-bit (final).
https://microsoft.productorder.com/clientx64/default.aspx
More info here: http://www.microsoft.com/windowsxp/64bit/upgrade/default.mspx
https://microsoft.productorder.com/clientx64/default.aspx
More info here: http://www.microsoft.com/windowsxp/64bit/upgrade/default.mspx