TOKYO, MAY 17 -- As if he weren't successful enough already, Microsoft Chairman Bill Gates today staged a spectacular launch of the latest Japanese version of his Windows software -- a product that could become a runaway hit in the world's second-largest PC market.

With a full-size orchestra blaring upbeat tunes, three projector screens showing Windows TV commercials, and purple and green laser beams glistening off the gold rims of his glasses, the floppy-haired Gates stood before a packed house in a huge exhibition hall and proclaimed: "Windows is the future."

In Japan, at least, that statement is hard to contest, given the striking supporting cast Gates took along today. The presidents of all the major Japanese PC makers, plus the heads of International Business Machines Corp. and Compaq Computer Corp., all promised to offer Japanese Windows as standard equipment on their PCs here.

This should give Microsoft a near lock on the "operating environment" market and a leg up in selling application software for Windows-based PCs. That, in turn, should help other U.S. software firms sell their products in Japan.

In America, Windows 3.1 was a relatively minor upgrade of the hugely successful version 3.0. In Japan, 3.0 was a flop. It quickly gained a nasty reputation for being "buggy" -- that is, full of programming errors that meant the software did not work as advertised. As a result, while Windows sells about a million copies per month in the United States, less than half a million copies of version 3.0 have sold in Japan over the past two years.

But version 3.1 is something completely new, and the product known here as "Ween-doe-zoo" could shake off its negative image. Virtually every computer magazine in Japan has Windows 3.1 on its cover this month, and the stories seem to agree that this new version is one that will soon be sweeping Japan.

"There are a lot of signs that this one will be the big success," said Katsushi Shiga, an analyst for the Tokyo office of Dataquest Inc.

Another big plus for Microsoft was the announcement from Just Systems, a Japanese software house, that it will quickly turn out a Windows version of its "Easy Taro" word-processing program, the best-selling application program in Japan.

In its Japanese manifestation, Windows looks and works quite a lot like the American version, albeit with some cultural changes. The famous American "screen saver" program that shows flying toasters zipping across the screen has been replaced here by a program that shows falling cherry blossoms drifting down. The list of "fonts" on the pull-down menus includes type styles not only for Roman letters but also for Chinese "kanji" characters.

Also, the Japanese version of Windows offers more complete instructions than the U.S. version.

With these adaptations, Gates said confidently today, Windows is poised to score the kind of success in Japan that it has already seen in the United States and Europe.

"We'll be able to expand the market considerably," the American billionaire told a jammed press conference here. "This is an opportunity for everybody to grow in this market."

Separately in Seattle, Microsoft said it plans to align office equipment makers behind a digital format that could extend its Windows software to facsimile machines, telephones and copiers. A spokeswoman said the company plans a June 9 announcement with a broad array of equipment makers aimed at unifying office machines behind a single standard.