WASHINGTON _ The New Economy is on trial here along with Microsoft Corp. Sure, the company is the one in the dock. Every contract, combination in the form of trust or otherwise, or conspiracy, in restraint of trade or commerce among the several States, or with foreign nations, is hereby declared to be illegal. SAN FRANCISCO _ In a recent move that indicated he has no intention of backing away from his company's aggressive business tactics, Microsoft Corp'.s chairman, Bill Gates, has proposed acquiring the software business behind 3Com Corp'.s popular Palm Pilot hand-held computer, according to people who have been briefed on the discussions.