Fox won the Nielsen derby last week among adults 18-49 on the strength of American Idol, My Big Fat Obnoxious Fiance and That '70s Show all of which finished in the top 20. CBS, buoyed by CSI, Survivor: All Stars and the Grammy Awards, ranked second in that demo but first among total viewers. The top five shows last week were American Idol (Tues.), CSI, American Idol (Wed.), the Grammy Awards and Friends. Reba, meanwhile, finished 91st for the week. Now that's what I call a family emergency.