The president-elect looks to reassure the financial markets and the public with swift Cabinet appointments and aggressive policy plans. By Peter Wallsten Reportingfrom Washington -- With a series of forceful actions in recent days,amid an almost unprecedented set of challenges, Barack Obama has takenan unusual step for a president-elect: attempting to alter thecountry's perilous course even before he takes office.The most dramatic example came Saturday, when Obama announced a far more aggressive economic stimulus planthan previously promised -- a two-year program to add 2.5 million jobsthat he said represented "an early down payment on the type of reformmy administration will bring to Washington."That announcement was the latest indication that the president-electhas decided to use the transition period to influence events at a timeof crisis, when the current administration appears powerless to stop aslide. "There's no question that Bush is still president, but people arelooking for signs to see what's going to happen going forward," said anObama aide who, like others, requested anonymity when discussingdeliberations inside the transition. "We're going to attempt to do thatin this period." Obama has moved with unusual speed to fill most of his top White Housestaff positions. And over the last week, he settled on a number of keyCabinet appointments designed to remove the uncertainty that hassparked turbulence in the financial markets and to replace it with asense of confidence in the administration-in-waiting. He offered theall-important job of Treasury secretary to a pragmatic and experiencedregulator, Timothy F. Geithner, and reached out to former campaignrival Hillary Rodham Clinton, an experienced figure known around theworld, to be the country's top diplomat. After the Geithner selectionwas reported Friday, the Dow Jones industrial average soared nearly 500 points. On Monday...