Games are missing from the My Games tab

http://support.steampowered.com/cgi-bin/steampowered.cfg/php/enduser/std_adp.php?p_faqid=86

I am logging in to Steam for the first time - where are my games?

If you purchased a retail package and created a Steam account, you will need to register your CD Key to activate the product. Please see the Activating a Product on Steam article for more information on registering a CD Key / activating a product on Steam.

I have logged into Steam before, but when I log in now my games are missing - what happened?

If you have already activated and played games on Steam in the past but the games are no longer appearing in your list of activated games, you are most likely logged into the wrong Steam account.

Please see the Contacting VALVe Billing and Support topic for instructions to reclaim an old account.