これを見てください:
http://msdn.microsoft.com/en-us/library/windows/apps/windows.applicationmodel.packageid.architecture.aspx
var architecture = packageId.architecture;
var package = Windows.ApplicationModel.Package.current;
var packageId = package.id;
var version = packageId.version;
var output = [ "Name: \"" + packageId.name + "\"",
"Version: " + version.major + "." + version.minor + "."
+ version.build + "." + version.revision,
"Architecture: " + packageId.architecture,
"ResourceId: \"" + packageId.resourceId + "\"",
"Publisher: \"" + packageId.publisher + "\"",
"PublisherId: \"" + packageId.publisherId + "\"",
"FullName: \"" + packageId.fullName + "\"",
"FamilyName: \"" + packageId.familyName + "\"",
"IsFramework: " + package.isFramework ];