By Katie Marsal

Published: 10:30 AM EST

Best Buy Co. said Wednesday that it has agreed to expand a pilot program aimed at testing sales of Apple's Mac computer line to approximately 200 of its stores by the fall.

The largest U.S. consumer electronics retailer confirmed the move during a quarterly conference call in which it said fourth-quarter earnings rose 18.5 percent, helped by a combination of strong sales of big screen TVs, install services, and an extra week in the quarter.

Best Buy said net income for the quarter ended March 3rd rose to $763 million, or $1.55 per share, up from $644 million, or $1.29, during the previous year. It added that revenues also increased 21 percent to $12.9 billion, with same-store sales rising 5.9 percent.

The expansion of the Mac pilot to 200 stores will represent a fourfold increase in exposure for Apple at the electronics retailer, which until now had been testing sales of Apple's PC line at only about 50 locations nationwide.

Best Buy initiated the pilot last June at a handful of stores located on the west coast but indicated that it would rapidly expand the program to more of its 900+ shops if the concept proved successful. Over 45 additional locations were later added to the mix in October.

Investment bank Morgan Stanley has said that a full expansion of the pilot to all of Best Buy's stores could generate as much as $400 million in additional Mac sales for Apple each year.

The Cupertino-based Mac maker is also running a similar, albeit smaller, pilot at Circuit City retail outlets located on the east coast.