Reviving Dead Gamertags for Use
Starting today, Microsoft have begun the process of making previously used and unavailable (dead) Xbox LIVE Gamertags available. This process will take some time to complete, and no we cant tell you when the Gamertag you want might be available. If you are interested, you should check back regularly as we are reviving Gamertags daily.
Sign into Xbox LIVE and go to the My Xbox channel, then select Change Gamertag. From here you can either choose from the random name generator, or you can enter a specific Gamertag to see if its available.
Changing your Gamertag does not affect your Gamerscore, Achievements, or your friends list.