I don’t have an Xbox 360 but I have made a gamertag on xbox.com. It is a silver membership. I am going over to my friend’s house and want to sign in with that gamertag I have made. Is it possible to sign in at my friend’s and get my gamertag upgraded to gold membership and only use that gamertag whenever i’m at his house? P.S. I have no xbox 360 harddrive or mem. card to transport my gamertag.