1.)First what you will need is a retail that has no memory at all and has been updated to the latest dash.

2.)Have a usb that has been configured with your xbox
and has one Xbox live account on it nothing else but your account no updates.

3.)Take that usb plug it up to your retail..
Make sure you have nothing else plug into your retail
except the usb and there should be no updates on the usb either. When you turn it on there should be no avatars but your xbox live account.

4.)Sign-in to your xbox live account it should ask for a update press yes and you should be getting updated and avatar updates to when it's complete.

5.)Unplug your usb. Plug it in your Jtag Console turn it on and there you go you have avatar updates on your jtag.

Note: If you have a jasper with MB Memory it may not save updates on usb it will put it in the console Menory instead. And also this will not let you CONECT to LIVE.