Click on Start -> Run, and type dxdiag. If a Windows dialog box is displayed


asking if you want to verify your drivers, you can safely click no and continue. When the program has
finished loading, you should see something similar to one of the following images:

Click Here to Zoom

Note that the Operating System line, refers to Windows x64 or 64-bit  or 32bit edition

this is located just right above the button Next Page, Save All Information, Exit down at the bottom of the window, click the sample icon to enlarge

The last window specifies the processor Itanium, which is a 64-bit processor.