UnitedHealth Group Inc. has hired Larry Renfro to take over as chief executive officer of its Ovations unit and executive vice president at the parent company.

Renfro succeeds Simon Stevens, who will continue to be a UnitedHealth executive vice president and now will oversee health reform and international initiatives.

Ovations oversees UnitedHealth’s Medicare business.

Renfro previously was president of the Fidelity Developing Businesses unit at Fidelity Investments, Boston, He also has been president of AARP Services Inc., an arm of AARP, Washington.

In other personnel news:

- Massachusetts Mutual Life Insurance Company, Springfield, Mass., has promoted Tom Cremona to be vice president of client relationship management.

Cremona succeeds Marie Augsberger, who has left the company.

Cremona previously was northeast division sales manager at MassMutual.

The retirement services division at MassMutual has hired Karen Buoniconti, Jim Keating and Eric Sarrazin to be relationship managers in a unit that works with third party administrators.

- Great-West Retirement Services, Greenwood Village, Colo., a unit of Power Corp. of Canada, Montreal, has hired Mike Demler to be sales director for western Michigan and Trevor Silveria to be sales director for central and southern Virginia and the state of West Virginia.

Demler previously worked for a unit of Hartford Financial Services Group Inc., Hartford.

Silveria has worked for Hartford and for MFS Investment Management, a unit of Sun Life Financial Inc., Toronto.

- American International Group Inc., New York, has named Monika Machon senior vice president and chief investment officer.

Machon succeeds Win Neuger, who will continue to be the company’s investments chairman and lead the external client asset management businesses that AIG intends to sell.

Machon has been the global head of fixed income for AIG investments and chairman of the board of AIG Investments Europe Ltd.

Jeffrey Hurd, who has been AIG investments senior managing director, chief administrative officer and general counsel, will be senior vice president and head of asset management restructuring.

- Craford & Craford Inc., San Rafael, Calif., which does business as Craford Benefit Consultants, has hired Scott Beeber as managing director, business development.

Beeber previously was a senior consultant for client developnent in the San Francisco office of Watson Wyatt Worldwide.

Beebe has a bachelor’s degree in international business finance from George Washington University and a master’s degree in management from Nova Southeastern University.