Using x64 hardware does not necessarily require that a 64-bit Operating System be installed. Because the x64 architecture is an extension of the x86 architecture, all x86-based Operating Systems will install and run natively as a 32-bit Operating System and as such is considered a supported state.
Using IA-64 hardware is not supported at all as this hardware is a completely different architecture that does not run 32-bit Operating Systems.
Carsten Siemens edited Revision 2. Comment: Added tag: has comment
Support for 64bit Windows is available in version 6.3 - see KB Article
support.microsoft.com/default.aspx
thanks,