Microsoft is seeking 30 companies, each with at least 5,000 PCs, who are willing to sign up and install on employees’ computers a small program — a “browser helper object” — that will count the number of searches performed with Microsoft Live Search.

The notion that a lagging search engine would offer monetary incentives directly to end users is not wholly new. A year ago, Yahoo appeared to be readying a rewards program for its search users that would be offered first to Yahoo Mail customers. A Yahoo survey, asking what would entice e-mail customers to designate Yahoo as their primary search engine, offered ideas like five free music downloads a month, a discount to Netflix, or 250 frequent-flier miles each month that could be transferred to most major airline mileage programs.

After completing the survey, Yahoo decided not to start the service. Whether it had discovered that its own e-mail customers withheld enthusiasm for the idea of making Yahoo their default search engine is not known. A company spokeswoman last week declined to discuss the survey or the subsequent decision to abort the plans for a rewards program.

Microsoft also tested the idea of rewarding search users last year, when its MSN unit put up a promotional Web site, “MSN Search and Win,” which provided instant prizes ranging from a Starbucks gift certificate to a Panasonic high-definition television. The promotion lasted about five months and, according to Mr. Sohn, “drove tens of millions of queries and for a relatively small amount of money.”

Both Yahoo and Microsoft’s MSN were thinking about the problem of customer acquisition in the same way. But Microsoft’s new program brings an entirely new approach to acquiring customers: buying them at wholesale, instead of retail. Microsoft need only persuade the I.T. department in order to achieve broad adoption at a large company, rather than slogging, cubicle by cubicle, to win loyalty one employee at a time. If the employees prove recalcitrant and continue to use “the incumbent,” that will be for I.T. to handle.

Microsoft, stuck in distant third place and losing ground to the leader with every lap, should realize that the airlines’ frequent-flier programs may not work well as a model for the software business. Mara Lederman, an assistant professor of strategic management at the University of Toronto who has closely studied the airlines’ programs, said one feature that has been essential to their popularity among business travelers is that customers earn the rewards but do not pay for the product — their employers do.

“If the fare for your preferred airline is $100 more, you don’t care because you don’t pay,” she said. “You just want the points because you want to take the family to Hawaii.”