Reverse Fax Number Lookup tool is here to help you identify the owner of the fax number that you need looked up to confirm if it's really the person or business you are trying to communicate with. View their recently played xbox games, achievements and more. How would I go about making a program to check if an xbox live gamertag is available? I want to be able to input a.txt file and the program will go through all the gamertags and make a.txt with the gamertags that are available.