By Hiawatha Bray, Detroit Free Press Knight-Ridder/Tribune Business News

Apr. 3--I once heard of a library that found a manuscript by Leonardo da Vinci that had been missing for a few centuries. It turned out the book was there all along, but on the wrong shelf. Since no one could find it, for practical purposes the book had ceased to exist.

Moral: All the information on Earth is useless unless you can find it. Which brings us to the Internet. It's the world's largest public library. But it has no central catalog - no simple way to sort through to find what you want. And unless you know exactly where to go, most information on the Net might as well not exist.

Worse yet, the Internet is full of information that never passed under an editor's beady eyes. How do you know it's accurate information? Often you don't.

Right now, thousands of people are signing onto the Net, thinking it's a cheap way to research almost any topic. But they soon see that finding trustworthy info isn't cheap or easy.

Just ask Leonard Fuld. He runs an international company that specializes in ``competitive intelligence,'' the art of figuring out what your business rival is up to. he collects information from public sources and studies it for keys to a competitor's business strategy.

So Fuld must practically live on the Internet, right? Not hardly. In his book, ``The New Competitive Intelligence'' (Wiley, $24.95), he doesn't even mention the Internet as an information source.

Not that Fuld is some kind of Luddite. He uses the Net - just not that much. ``Overall it's a tool that companies can't ignore and shouldn't ignore,'' he says.

But he prefers commercial database services such as Nexis and Dialog. These are expensive, but the information is well-organized and comes from reliable sources. ``What most folks don't realize is that the Internet takes a lot of work and a lot of information savvy to make use of,'' said Fuld.

So let me offer a little savvy. There are effective ways to find valuable information on the Net. In coming weeks, I'll share some.

Let's start with Usenet. It's one of the most popular features of the Internet, and is also available to users of CompuServe, Prodigy and America Online.

Usenet is a collection of several thousand ``newsgroups,'' or bulletin boards. Each is devoted to a topic, such as Macintosh computers or Christianity or stamp collecting.

The trouble is that anybody can post messages on most newsgroups. The writer may know the topic inside-out, or may just be some moron with a keyboard. You can't completely trust Usenet stuff.

Suppose you want to learn about computer hacking. You could begin with a visit to alt.2600. This newsgroup is a popular hangout for hackers or hacker wannabes, and it's a good place to spot the latest fads and rumors among the computer underground.

But the news on this newsgroup is extremely unreliable. Many of those who hang there are the sort who'd be spray-painting graffiti if they didn't own modems. You'd be a fool to completely trust information you find on alt.2600.

On the other hand, there's a group called comp.risks. It specializes in tracking the dangers posed by misuse of high technology. Messages on comp.risks are crammed with information about computer hacking, viruses and other unpleasantness. Better yet, they include references to books, magazines and newspaper articles, so you can double-check the facts.

Most people who post messages there are academic experts on computers or other technologies, or they work for high-tech companies. They sign their names and include E-mail addresses, so you can track them down for more information. Usually they're happy to answer questions.

Why is comp.risks such an orderly place? Because it's a moderated newsgroup. That means an expert in the field reads every incoming message before it is posted to the group. If a message is poorly written or lacks factual support, it never sees the light of day.

If you're researching a particular topic on-line, try to find a moderated newsgroup on that subject. There are about 900 such newsgroups, covering a wide range. As you might expect, most focus on technical discussions of computers. But the other sciences are well represented. There are also moderated groups on religion, art, history, science fiction and many more subjects. There's even a group called news.lists that has a complete list of moderated groups.

Even stuff in moderated newsgroups shouldn't be treated as holy writ. But it tends to be far more reliable than the usual Usenet chatter.

Still, don't give up on unmoderated newsgroups. They have their uses. Many people include their names and E-mail addresses in messages. So you can write to someone who seems knowledgeable about a particular topic.

Or you can just send out a call for help. Find an unmoderated group that deals with the topic you're researching. Then post a message asking for more information. Leave your name and E-mail address, and maybe a phone number. Chances are, a few people will get back to you, and some may know what they're talking about.

I routinely hunt for information on Usenet, and I've never come away empty-handed. It's just a matter of knowing how.

BY THE BY, Microsoft Executive Vice President Mike Maples was in Detroit on March 24, showing off Windows 95 to a gathering of black engineering students. They oohed and ahhed at the right places, and were pleased when Maples said Windows 95 would hit the street by August.

That very afternoon, InfoWorld magazine reported that the most recent version of Windows 95 contains a major bug that causes it to crash while running several programs at once. The article suggests it could take a lot of extra work to solve the problem, even though it quoted a Microsoft official who stands by the August release date.

Will IBM exploit the latest Windows 95 glitch? They'd better - IBM's rival OS/2 software is so far behind in sales that Big Blue can't afford to be gentlemanly. I expect to see a lot more OS/2 commercials in the next few weeks.

You can send electronic mail to Hiawatha Bray. If you're on the Internet,

send it to: watha(at); on Compuserve, write to: 72662,2521; America Online users, write to: WathaB. END!A3?DE-TECH-COL

AP-NY-04-02-95 1403EDT This material is copyrighted and may not be republished without permission of the originating newspaper or wire service. NewsHound is a service of the San Jose Mercury News. For more information call 1-800-818-NEWS.