The WB network will present the first look at a full-length trailer for “Harry Potter and the Chamber of Secrets” Thursday during the 8 p.m. premiere of “Family Affair,” Reuters reports. Though previews of “Secrets,” due to open Nov. 15, have been playing in movie theaters, this is the first full-length clip — 2 minutes, 17 seconds — of the much-anticipated sequel to last year’s $300 million-plus hit “Harry Potter and the Sorcerer’s Stone.”