One month after Christa Davies joined Aon Corp. in November as executive vice president of global finance, the Chicago-based company reinvented itself. The sale of two underwriting units for $2.75 billion allowed Aon to exit the lower-margin, capital-intensive business and focus on its risk brokerage and consulting services. It's a whole new ball game for finance.

Now, as Davies prepares to move into the CFO slot in March, she's planning a finance department reorganization to reflect the new focus on professional services and increased reputational risks. "We will review responsibilities post-sale and streamline areas where we no longer need underwriting expertise," says Davies. She's replacing David Bolger, who is leaving to work on Chicago's bid for the 2016 Olympics.

Davies, 36, knows something about reinvention. The native Australian planned a career in aerospace engineering, penning her undergraduate thesis on fuel-efficient ways to power spacecraft using the gravitational pull of planets and stars. But U.S. defense budget cuts and consequent industry layoffs her senior year led her to conclude her future lay elsewhere. "Aerospace didn't seem like a wise move at the time, and I also decided it wasn't a good idea to become so specialized so early in my career," she says. Instead she landed a Fulbright scholarship that paid her way to a Harvard M.B.A.