On the rolling fields of Fauquier County outside of Middleburg the horse is king, and computers are vassals that should know their place -- which is preferably in the city.

Or so say some residents who are opposed to a plan by a Reston-based computer technology firm to use a historic estate nearby Middleburg as a training and conference facility.

Owners of the firm, Advanced Technology Inc., have promised to place 17 restrictive covenants on their use of the 108-acre estate to soften the facility's impact on the rural community. The covenants would prevent the company from using the surrounding land for any purpose other than for agriculture, from constructing anything on the property other than a 40-car parking lot and two tennis courts, and from altering the exterior of the house, called Boxwood.

But this month, the county planning board recommended denial of the firm's application for a special exception permit, and the county board of supervisors has tabled its decision on the application after a vocal public hearing attended by dozens of concerned residents.

"The feeling by the board and those at the public hearing is that a conference center, no matter how nicely done, is not in keeping with the area," said County Planner Richard E. McNear, who said the Fauquier master plan stipulates that Boxwood and the surrounding area be used solely for agricultural purposes.

Robert M. Darby, vice president of Advanced Technology, said the company chose Boxwood after searching for a site for several months. The company, which develops engineering and computer programs for the government and private industry, has a $2.1 million contract to purchase the former horse farm from owner Stephen C. Clark contingent on receiving a special exception.

"We were looking for a place that would give us freedom from office buildings and our day-to-day work environment," Darby said. "If you have seen Boxwood, then you know why we are attracted to it."

For many of the neighbors, though, Advanced Technology would set a precedent no matter how quiet and unobtrusive it was.

"On the face of it, this doesn't look intrusive, and it may even appear that we are being unreasonable," said George A. Horkan Jr., an attorney hired by some landowners to fight the special exception permit. "But if you look beyond the immediate, you will see that it sets in motion a most incompatible precedent."

Horkan said landowners are concerned with a list of "what ifs" that includes: What if Advanced Technology is bought by a larger company; what if it decides to subdivide the property after the covenant expires 10 years hence; and what if another firm buys property in the area and points to Advanced Technology when applying for the next special exception permit?

"If the board grants a special exception permit now, then how does it deny another five years down the road?" said Horkan. "This area is much too fragile, much too important historically and to the thoroughbred horse network to take risks."

Darby said the covenants would remain even if Advanced Technology, created nine years ago, were to be bought by another company. He also said the firm is willing to enter into a legal agreement that will give right of first refusal to a Virginia agency responsible for saving open space should Advanced Technology ever decide to sell Boxwood.

"They are obviously a nice company, but it doesn't matter what they agree to," said Horkan. "The point is we are opposed to any commercial use, no matter how unobtrusive."

Horkan said Boxwood could be sold to other horse breeders or farmers. "This is not a white elephant," he said. "It was on the market all of three days."

Owner Clark could not be reached for comment.