How to move your GamerProfile from your HDD to your USB.

1. On your Xbox 360 dashboard, go to My Xbox and then select System Settings.

2. Select Memory

3. Select the storage device that has the gamer profile (Hard Drive)

4. Select Gamer Profiles.

5. Select the gamer profile you want to move (Your XBL gamer profile)

6. Select Move.

7. Select the storage device you want to move your gamer profile (Memory Unit/USB)

8. Confirm the game profile move.

Simple as.