Is my i7 920 Intel processor considered ia64 or x64?

ia64 is a reference to the relative flop that is Itanium.

The i7's use x64, aka: amd64 or x86-64, or Intel 64 (EM64T). They all refer to essentially compatible 64-bit extensions. For more info on those, check here

x64

ia64 refers to Itanium based designs and their brethren.

x64. ia64 is the Itanium architecture which is found mostly on enterprise class servers.