The co-chief executives don't seem to be able to figure out a strategy that will keep them ahead of the rivals.
Mr. Micheletto, a former co-chief executive, will also continue as chief financial officer.
He retained his roles as co-chief executive and director.
He returns to the chief executive position after stepping down as co-chief executive in May 2003.
Mr. Lee's early resignation as co-chief executive had become widely expected.
She holds the titles of co-chief executive and president.
He was named a co-chief executive in 1992 and chief executive in 1994.
Many workers in the company referred to her as the "co-chief executive".
After the merger, the men say they will be co-chief executives with equal footing.
He was named co-chief executive in 1992 and sole chief executive two years later.