So you've loaded Medical HouseCall onto your computer - either through four floppies or a CD Rom - and you're ready to try out its "interactive home medical guide and symptom analysis."

Now what?In Windows, use the mouse to click on the icon for the program and a disclaimer immediately pops up. Click on that and a colorful menu appears with options for a tour, symptom analysis, drug interactions and medical records, as well as an encyclopedia.

You can use the index to look up a problem directly.

Throughout your session, options provide ways to trace key words for more information about particular subjects, or return to the previous menu.

First the program will prompt you for information needed for an extremely basic profile: name, age, sex. It heeds this, because if you're a male but are nosy enough to click on an icon about female problems, it'll tell you to get lost.

Next comes a menu for 19 symptom categories, plus the index: head, face and neck; ears and hearing; mental changes; kidney and urine; heart, chest and circulation; eye and vision; nose, throat and mouth; trunk, back and pelvis - plus other areas.

For many questions, handsome graphics are supplied.

Recently I suffered back pain, although it's mostly gone now.

Trying to learn more about it, I clicked on the "trunk, back and pelvis" categories. Medical HouseCall presented a short list of yes-or-no questions to narrow down the cause.

Pain in the lower back? Yes. I plow through the list. If there isn't enough information for the program to offer any suggestions, I request follow-up questions.

After a few minutes, the program suggests that I may have nonspecific back pain - the odds favoring this seems about 65 percent, with other causes listed in decreasing likelihood. The next highest listing, ankylosing spondylitis, is frightening, but at 19 percent I don't pay a lot of attention to it.

Besides, according to HouseCall, AS has other symptoms that I lack - notably, a loss of appetite. Also, while I stoop for a lot of things, I never resort to "chronic stooping to relieve symptoms."

Back I turn to the most likely culprit, which is something of a catch-all: pain in the back from an unknown cause. An analysis tells me that it could stem from muscular strain, injury to the back, overuse, muscular disorders, etc.

The analysis cites causes, incidence and risk factors; symptoms; signs and tests that doctors can order; treatment; expectations; complications; and notes about calling my health-care provider.

Under expectations, the program is reassuring: "Most cases of back pain will resolve without other intervention," it says.

"It is helpful to sleep on a very firm mattress (with a bed board under the mattress), or a waterbed, or even the floor. Heat or ice applied to the affected area may provide some relief."

Medical HouseCall lets you print the information with a click of the mouse, always reminding the user that the product is "for informational purposes only and (that it) should never be used as a substitute for seeking professional medical treatment and care."

Elaine M. Bailey, president and CEO of Applied Medical Informatics - the Salt Lake company that developed and is marketing the product - pointed out that it can analyze drug interactions.

"You can enter the drugs that have been prescribed for you before you take them, and check to see whether there are any dangerous interactions or side effects," she said. "You can also test this against alcohol, caffeine, and it always includes pregnancy." A pregnant woman can find out if a particular drug could be harmful to the fetus.

A doctor who prescribes tetracycline might not know that the patient is taking a common over-the-counter medication for acid indigestion, Bailey said. But the combination of tetracycline and magnesium (which may be a main ingredient of the antacid) could cause a serious complication, she said.

HouseCall will warn the user about that, she said. Just check for drug interactions.

"It's a real self-protection thing. You do it before you fill the prescription, and you do it before you combine the prescription with an over-the-counter drug."