As AOL Time Warner (AOL) stock fell for the first time below $20 a share and just two days after naming Chief Operating Officer Bob Pittman to run the Internet division, the media behemoth found an old radio executive to run the limping Web site. 

The company named James de Castro, a former chief executive officer of AMFM Radio Group, president of AOL Interactive Services. He replaces Jonathan Sacks, who retired in February. 

Though Pittman will effectively be in charge of the AOL division, it's expected that de Castro, 47, will serve in a hands-on role controlling the company and running the flagship AOL service, which has more than 34 million subscribers. 

He's expected to help build up the sagging subscriptions and advertising revenues under incoming CEO Dick Parsons. 

De Castro will report to AOL Chief Operating Officer Michael Kelly, who reports to Pittman. 

Pittman, who also retains his chief operating officer titles with parent AOL Time Warner, will need the time that de Castro can provide him to oversee the entire AOL unit, including Netscape and the CompuServe Web service. He will also still be responsible for units such as film and TV divisions. 

The news had little effect on the sagging AOL Time Warner stock, which fell $1.10 to close at $19.60, down 5.3 percent. 

De Castro lauded Pittman for "building teams" that would help right the listing firm. 

"Don't be confused that Jimmy de Castro is coming in to take over for Bob Pittman," de Castro said. "I want to enhance what they have, to be able to deliver our product." 

De Castro was nostalgic about his beginnings in Chicago radio, where he said Pittman was discovered early on as a disc jockey. 

"I kind of like being associated with Bob Pittman's name," he said. "He was in Chicago radio, too."