As the weight of computers edges under six pounds and their value tops the price of a used car, thieves are loading up on the eminently stealable instruments by the armfuls. In 1992 computer theft increased at least 4-fold since 1991, estimates John Hastings, president of the American Computer Exchange (AmCoEx), a used-computer brokerage in Atlanta. Robert Zises, president of the National Computer Exchange (Nacomex), a similar enterprise in New York City, reckons the increment is closer to 10-fold.

Until recently, secondary-market channels like AmCoEx and Nacomex were unwitting fences of purloined electronics. Now, in independent but almost identical efforts to curb the flow of stolen hardware across their trading floors, each has established a registry of pilfered PCs. Anyone who suffers a loss can phone in the missing item's make, model, and serial number. The numbers are disseminated across the country, shutting down thieves' traditional sources of quick-and-easy cash. The databases serve also to reassure prospective used-equipment buyers, who can phone in to verify that given serial numbers aren't on the lists. Already, stolen goods are getting reunited with their rightful owners. When a corporate laptop recently was lifted from a Ciba-Geigy employee's car in a New York City suburb, the company wrote off the theft as just another statistic. But its distressed employee phoned the loss in, anyway. Sure enough, the portable was offered for sale a week later at a Nacomex outlet, where brokers foiled the theft.

To file a stolen-computer report (be sure to keep a record of serial numbers), to query for stolen-property listings, or to get more information, call Nacomex's Stolen Computer Registry (212-777-1291) or AmCoEx (800-786-0717).