BTW, you should be careful with CPU detection. If you create a single app package that targets multiple CPUs, the certification process will make sure that all users have the same (good) experience. If you need to create different experiences for different processors, you need to create different packages per processor. Here's the way the certification requirements state it...
3.3 Your app must provide the same user experience on all processor types that it supports
If your app has a different user interface or functionality when it runs on different processor types, you must submit a separate app for each processor type and describe the differences in the Description of each app.
You can find all of the Windows 8 cert reqs here: msdn.microsoft.com/en-us/library/windows/apps/hh694083.aspx