This post details how to use DeviceExtendedProperties and UserExtendedProperties classes from the Microsoft.Phone.Info namespace to find a WP7 device manufacturer, device unique Id and users Anonymous Windows Live ID as follows:

To be able to obtain the Device Unique ID and Windows Live Anonymous ID you must first add the capabilities to do this to your WMAppManifest.xml file within your WP7 project as follows:

    <Capabilities>
      ...
      <Capability Name="ID_CAP_IDENTITY_DEVICE"/>
      <Capability Name="ID_CAP_IDENTITY_USER"/>
      ...
    </Capabilities>

One important point to note is that you should only really use the device unique id and anonymous windows live Id in your application if really requires it. The reasoning on msdn is as follows:

DeviceExtendedProperties requires the device identity capability. If your application uses this class, the user will be alerted that the application requires access to the device identity when viewing your application on Windows Phone Marketplace. For this reason, it is recommended that you use this class only if your application requires it.

Note: In the example below the manufacturer is returned from GetManufacturer without needing to list the device identity capability within the WMAppManifest but if you tried to get the device Id onr anonymous Id without the capability it will throw an UnauthorizedAccessException.

The following code example demonstrates how to retrieve the Device Manufacturer, Device Unique ID and Windows Live Anonymous ID

using Microsoft.Phone.Info;
namespace NickHarris.Net
{
    public static class ExtendedPropertyHelper
    {
        private static readonly int ANIDLength = 32;
        private static readonly int ANIDOffset = 2;
        public static string GetManufacturer()
        {
            string result = string.Empty;
            object manufacturer;
            if (DeviceExtendedProperties.TryGetValue("DeviceManufacturer", out manufacturer))
                result = manufacturer.ToString();

            return result;
        }

        //Note: to get a result requires ID_CAP_IDENTITY_DEVICE
        // to be added to the capabilities of the WMAppManifest
        // this will then warn users in marketplace
        public static byte[] GetDeviceUniqueID()
        {
            byte[] result = null;
            object uniqueId;
            if (DeviceExtendedProperties.TryGetValue("DeviceUniqueId", out uniqueId))
                result = (byte[])uniqueId;

            return result;
        }

        // NOTE: to get a result requires ID_CAP_IDENTITY_USER
        //  to be added to the capabilities of the WMAppManifest
        // this will then warn users in marketplace
        public static string GetWindowsLiveAnonymousID()
        {
            string result = string.Empty;
            object anid;
            if (UserExtendedProperties.TryGetValue("ANID", out anid))
            {
                if (anid != null && anid.ToString().Length >= (ANIDLength + ANIDOffset))
                {
                    result = anid.ToString().Substring(ANIDOffset, ANIDLength);
                }
            }

            return result;
        }
    }
}

Other Extended Device information that can be retrieved using this class are:

DeviceName
DeviceUniqueId – if you are after an id to identify the user you should not use this, use Microsoft.Phone.Info.UserExtendedProperties with a parameter of “ANID”
DeviceFirmwareVersion
DeviceHardwareVersion
DeviceTotalMemory
ApplicationCurrentMemoryUsage
ApplicationPeakMemoryUsage

More details on these extended properties can be found here

Nick