In an extraordinary move, NBC has completely revamped the fall schedule it announced only last week after seeing what its broadcast rivals had done.

NBC moved "Law & Order" to Friday nights, took "Medium" off the schedule until midseason and shifted its highly touted Aaron Sorkin show on the backstage world of a TV comedy from Thursday to Monday.

While it's not unusual for networks to make minor tweaks to a schedule between the time it is announced and when it goes on the air, this is the first time in memory a schedule has been completely revised. NBC made changes on every night but Saturday.

"We go first and we're in fourth," said Kevin Reilly, NBC entertainment president. "Unusual circumstances lead to unusual measures."

Following tradition, NBC last Monday was the first broadcast network to announce its fall schedule to advertisers. That was no problem during the years NBC dominated in the ratings; its rivals reacted to its plans. For the last two years, however, NBC has finished in fourth place behind CBS, ABC and Fox.

When ABC moved its hit drama "Grey's Anatomy" to Thursdays, that set the dominoes tumbling for NBC. It had scheduled Sorkin's "Studio 60 on the Sunset Strip" for a time slot that suddenly included "Grey's Anatomy" and "CSI: Crime Scene Investigation."

So Sorkin's show was shifted to Mondays at 10 p.m., displacing "Medium."

On Tuesday, Wednesday and Thursday nights, NBC shifted away new series from the 9 p.m. hour in order to give them a better chance to get established. For instance, NBC had scheduled its new drama "Kidnapped" for Tuesdays at 9 p.m. anticipating Fox was going to move "House" to move to a new night.

Instead, Fox kept "House" where it was and NBC has decided to air "Law & Order: Criminal Intent" and "Law & Order: SVU" back-to-back starting at 9 on Tuesdays.

"Kidnapped" was moved to Wednesday at 10 p.m., which forced the move of "Law & Order" to Friday, a change not likely to please producers of the long-running legal drama. "Crossing Jordan," which was originally going to appear on Sundays after the NFL season ended, will instead start on Fridays in the fall.

Two new comedies that were supposed to air at 9 p.m. on Wednesdays will move up an hour, switching places with the reality show "The Biggest Loser."

NBC will also air the game show "Deal or No Deal" on Thursday in the slot vacated by "Studio 60."

In addition to keenly watching the schedules of his rivals, Reilly said he had seen the pilots of shows on other networks and that made him more confident about his shows, although he wouldn't say what he thought was weak elsewhere.

He insisted the NBC moves did not smack of desperation.

"I think it would be a little foolhardy to say, `we're moving in, let reality be damned,"' he said. "Let's realign with the schedule that in the light of day seems to make the most sense."