`ER' starts countdown to series' final flatline (AP)

Actors Linda Cardellini, left, and John Stamos are seen while filming an episode of 'ER' on set in Burbank, Calif. on Friday, April 25, 2008. The medical drama 'ER,' one of prime time's longest-running series, will expire next February. And 'ER's' upcoming 14th season-ender (10 p.m. EDT Thursday) will slide the show one step closer to its demise.  (AP Photo/Matt Sayles)AP - Deep inside Stage 11 on the bustling Warner Bros. lot, a giant of a television show is starting to die.