While the global economy may benefit from it, the Williamsburg Economic Summit could be either an economic boom or a bust for U.S. companies looking to push everything from potato chips to computer software to visiting journalists and diplomats.

Virginia's two major utility companies are worried that they may never recoup the costs of providing increased telephone and electric services to Williamsburg's swelled population during the three-day conference.

"We'll never recover some of our costs," said Paul Miller, a spokesman for Chesapeake and Potomac Telephone Co. "We had to install so many new phones that cables are running out of windows and wrapping around buildings like spaghetti."

The ninth Summit of Industrialized Nations, which officially begins Saturday, is projected to cost Uncle Sam close to $7 million.

As a cost-cutting measure, the White House called upon private businesses to donate products or services to help meet the demands of feeding and housing an expected 5,000 foreign statesmen and journalists.

More than 100 U.S. companies responded, seeking either good public relations or a promised tax break. Ford, General Motors, and Chrysler, for example, are donating more than 100 cars. IBM has loaned 75 typewriters, and Granny Good Foods of Oakland, Calif., is shipping 1,200 bags of Hawaiian-style potato chips.

For other large corporations, the conference is a chance to show off their latest electronic technology to government leaders of Britain, West Germany, Japan, Canada, France and Italy.

ITT-DialCom International Inc., which specializes in electronic mail, is donating an electronic bulletin board that will keep track of agendas and messages in every delegation room through a video monitoring system, officials said. American Bell Inc. will make available miniature electronic black boards to the heads of state for scribbing notes that will be automatically transferred to staff members in different rooms.

Time-Life Teletext says it is providing, free of charge, its electronic news service through TV sets in delegates' private suites. RCA Global Communications spokesmen said the company has donated 60 telexes and is installing hotlines for individual heads of state to their member countries.

But, unlike other communications companies that can easily ship back their equipment, C&P Telephone has dug deep and built high to prepare Williamsburg to communicate with the rest of the world during the historic summit.

In one of the largest projects it has ever tackled, C&P added 2,500 new circuits to the city's existing 11,000, as well as 25 miles of additional cable, three additional swtichboards and two 100-foot receiver towers.

And even when it collects its telephones after the conference, C&P will have a far more difficult time figuring out how to bill thousands of dollars of manhours and construction costs. So far, the federal government's tab on construction costs alone is more than $500,000, Miller said.

Wiring Williamsburg for additional electrical services is costing the government another $62,000, said the Virginia Electric Power Co. The utility plans to follow "normal billing procedures" to collect its fees, said a spokesman.

"We feel the benefits accrued from the summit will be for the nation as a whole, so the taxpayers can pay for it, not our shareholders," explained George Hudgins, Vepco's district manager in Williamsburg.

The central nerve center for the summit has been created out of a four-story basketball arena on the College of William & Mary campus. Transformed into a press center at a cost of more than $1 million, the arena will be the hub of electronic activity for journalists.

Maryland-based Gilbane Building Co. renovated the arena on a no-fee basis, which Gilbane regional manager William Choquette says saved the government about $200,000.

Existing classrooms, offices and four gyms were converted into eight separate briefing rooms, and services such as a post office and travel desk are being installed. The United Virginia Bank will operate a foreign currency exchange in the center during the conference using employe volunteers.

Meanwhile, many smaller companies are under government contract to provide everything from tents to trees. Avcom Audio Visual Services, a Rockville-based firm, has a $60,000 government contract to provide privacy booths and all electronic equipment, from microphones to a wireless video system, to aid interpreters during the rounds of meetings between heads of state. Since some of the meeting rooms are too small to hold both the delegations and interpreters, Avcom has installed a closed circuit television system so that negotiations can be monitored by translators from nearby rooms.

Sunset Hills Foliage, a Silver Spring florist, stands to reap a bonanza from the summit. The small company will provide 175 hanging plants, costing $12 apiece, and dozens of ficus trees, which stand about five feet high, to decorate the press tent, said Diane Lustman of Sunset, adding that "that is one heck of a large tent."