Senator Hatch observed that monopolists are subject to closer antitrust scrutiny than other companies and they have to be more careful in their business practices. After the hearing he characterized Microsoft as a monopoly and said the company ''will have to learn to live by the rules that govern monopolies.'' The Justice Department sued Microsoft last October, contending that the company was violating a 1995 consent decree with the Government by forcing makers of personal computers to load Microsoft's Explorer program for browsing the Internet's World Wide Web as a condition of licensing its Windows operating system, which is the industry standard. Microsoft asserts that Explorer is not a separate product but an ''integrated feature'' of Windows -- and thus an allowable improvement to the operating system under the consent decree. In December, a Federal judge issued a temporary injunction ordering Microsoft to offer PC makers the choice of taking Windows without Explorer. Microsoft is appealing that order.