Microsoft has announced that nearly 1 million old Gamertags that were abandoned for the original Xbox console will be made available for current Xbox Live Gold members to claim starting on Wednesday, May 18.
According to the Major Nelson site:
These Gamertags are from accounts abandoned from the original Xbox era, the same source of Gamertags we used in our 2011 release. These accounts never migrated to Xbox 360 and as a result they have been inactive for quite some time. While it may be challenging to find the exact Gamertag you want, keep trying, as there are many great Gamertags that will be released.
Some of those Gamertags include proper names, types of food, animals, pop culture references and more. They will be released over a 24-hour period starting at 2 p.m. Eastern Time (11 a.m. Pacific Time) on Wednesday. Xbox Live Gold members must be both currently active and have at least one cumulative year of membership to stake their claim on these Gamertags.