(FORTUNE Small Business) – Art Mellor drives a really nice Porsche, a metallic black Boxster S. It's a pretty car, a fast car. It rumbles when it idles, hums when it accelerates, a tangible reminder that in a former life Mellor, 40, was an entrepreneurial success: a cofounder of three companies, including Midnight Networks, a computer-network testing firm he sold to Teradyne in 1996 for $10 million. Mellor is a particular entrepreneurial type: honest ("brutally," says a friend), logical ("extremely"), and impatient. He admits to no motive beyond self-interest. He isn't always pleasant company. Even Mellor's best friend, Peter Schmidt, won't say he's a nice guy. "Um--if I had to pick one adjective, I wouldn't use 'nice,' " says Schmidt, 37, who co-founded Midnight

Networks with Mellor and presided at his wedding. "But he is very generous. And he is very considerate. Sometimes." Says Shari Agatstein, 35, another close friend (she and her husband accompanied the Mellors on their honeymoon): "He can really rub people the wrong way." When confronted with confused thinking or inconsistent behavior, Mellor bores in. "This is one of the things that people perceive as not very nice," says Schmidt. "He won't let go until he's no longer confused. He's not doing it to make people feel like idiots, but he's confused by their confusion and he doesn't want to be confused." Needless to say, he's brilliant. Just don't call him a genius, not within earshot. He's been known to reply, "To you I am."

Three summers ago, on June 14, 2000, Mellor got some scary news that left him briefly dumbfounded. At the time he was CTO of Gold Wire Technology, the network-configuration-management startup that followed Midnight Networks. He earned $180,000 a year. Gold Wire had just raised another $20 million in VC funding, an IPO was on the horizon, and while the market was down, nobody believed yet that it was down for the count. Plus, he was in love, soon to be married. The next thing he knew, Mellor was sitting in a doctor's office in Boston, waiting for his test results, actually hoping, he says, for a diagnosis of syphilis. No such luck. The numbness in his back and the sexual dysfunction were, it turned out, symptoms of multiple sclerosis, a chronic, degenerative disease of the central nervous system that shows up as lesions on the brain and spinal cord. About 400,000 Americans have MS, most of whom, like Mellor, are stricken as younger adults, in the midst of their busiest, most productive years.

Mellor's first thought was, I'm a smart guy, I'm still young. I'll go back to school and become a neurologist and discover the cure--until he realized that a lot of smart people are already doing that work, but it's not helping him. The more Mellor learned about MS, the madder he got. The madder he got, the more he complained. Complaining for Mellor is like breathing. It's how he fuels up for the next step. The reason he was never content working for somebody else was that he kept observing things that to him were just wrong--wrong products, wrong processes, wrong ways to run a company. His pal Schmidt was just as bad. They used to get together for lunch whenever they could and complain to each other. (They both have fond memories of those lunches.) After a while the pair just had to start their own company "so that we could prove that we could do it right," says Mellor. Because complaining without acting is just whining in Mellor's book, and he hates that. ("Well, why don't you do something about it?" is how he used to taunt his mother whenever she complained. Sweet kid.) "To just go, 'Gee, I hope somebody does something about this,' isn't an option for me," he says. "I have to be working on it."

To Mellor's entrepreneurial mind, the landscape of medical research resembled a bizarre world in which there were 1,000 companies making car parts and nobody assembling cars. That wasn't going to get him cured. What was missing, Mellor realized, was some way of directing all that potentially useful research toward results. Which is how Mellor came to quit the sexy world of tech startups and co-found--with his neurologist, Dr. Tim Vartanian--the Boston Cure Project.

The idea of Mellor's running a nonprofit takes some getting used to, even for Mellor. "Most people I've met who seem to be heavily into the nonprofit side of things are socially responsible," he says. "It matters to them that they do something that benefits society. I guess I'm a relatively selfish person. But I'm lucky to have a problem whose solution will help many other people. I can leverage that aspect of it."

He means leverage for his benefit; that's how Mellor's mind works, but that shouldn't surprise or disappoint anyone. Mellor's a thoroughbred. He enters the nonprofit world lugging the complete entrepreneurial package. Not just flashy presentations and the latest management techniques but a primal motive (self-preservation); a competitive streak to make gentler souls flinch; a big, hairy, audacious goal if ever there was one (Mellor really thinks he can cure MS); and ample hubris, of course--that being the peculiar madness of the tribe.

"I had a dream, a very vivid dream once, years and years ago," before having MS, says Mellor. "I dreamed that I got so frustrated with the slow progress in AIDS research that I injected myself with HIV so that I would have a motivation to solve the damn problem and stop being frustrated about it." If Mellor believes now that he can solve this damn MS problem, its victims will say: More power to him. So what if he thinks it's all about him?

As a kid, he found his favorite books were the ones that explained in detail how things worked. Later, as an undergraduate at MIT, Mellor absorbed the engineer's code, which is to say: You can fix anything, but not until you know exactly what's wrong. "I love the horrible truth over the beautiful lie," he says. "I want to know, 'How bad is it really?'" As soon as Mellor got his diagnosis, he plunged into the medical literature, starting with whatever he could find on the Internet, advancing to textbooks and professional journals that he borrowed from his doctor. What he found was mostly bleak. Nobody dies from MS--that's the good news. The bad news is that most people who have it will wind up in a wheelchair. Mellor's not there yet. His symptoms so far have been fatigue, depression, blurry vision, bladder problems, sexual dysfunction, and numbness, any of which can come and go. Mellor had been free of troubling symptoms for almost a year when, not long ago, he woke up with a tingling in his feet. Since then the numbness has risen like a tide, from the soles of his feet to his ankles to his calves and past his knees, a little higher each day. He draws a line with his fingers across both legs at mid-thigh to show where feeling stops. He can walk, he can press the pedals of his Porsche, but he can't feel anything.

MS has no known cause, an unpredictable course, and no cure. A few promising MS drugs have appeared during the past few years, but their effectiveness is spotty, they all have unpleasant side effects, and there's no consensus among doctors that any of them so much as slows the progress of the disease, much less cures it. A low point for Mellor was when he came across an entry in a 1932 encyclopedia that taught him nearly as much about MS as he had learned from his survey of the current literature. "I started meeting with researchers," says Mellor, "asking them, 'Am I reading this wrong?' They said, 'No, that's what it is.'"

Mellor's sudden interest in knowing all that was knowable about MS opened up a whole new world for him to complain about. He was appalled to discover how little money is spent in the U.S. on independent research that's even loosely related to MS. Last year it was about $125 million--easily outpaced by what Big Pharma spends annually to market its new MS drugs. Mellor then examined the largest private funder, the National MS Society, a half-century-old nonprofit with chapters in all 50 states that says its mission is "to end the devastating effects of MS." He found that the society has other priorities, such as advocacy, education, and support for MS patients and their families. Only 21% of the $168 million it raised last year went to research. That's a typical ratio, a fact that surprised Mellor at first, then made him angry. "They intentionally mislead people into believing that the money is going to work on a cure," Mellor says, still incredulous. ("The National MS Society provides hope and help for Americans with MS," responds a spokesperson. "Hope through our research programs and help through client programs that make daily life better for people with MS and their families.")

Having diagnosed the flaws in the MS market, Mellor set out to exploit its untapped niche. He raised cash--an estimated $500,000 in 2003, his third straight year of doubling donations--by being brutally straight with potential contributors about exactly what his organization is about. The Boston Cure Project is "dedicated to curing MS by determining the cause of MS," period. It offended Mellor as a manager to discover how little was being done to coordinate the research effort. The question he asked himself was, "How do we pull it together and make something that has some value here?"

"In many areas of nonprofit--but particularly in medical research--there's no middle layer," Mellor says. "There are people doing work, and people collecting money and giving it to those doing the work, but just imagine what the high-tech space would look like if people raised money and just gave it to engineers. Would you have any products? No, you'd have none. That's why we have very few products in the medical research world, in my opinion. There isn't this middle layer of people who understand what needs to happen."

From that insight emerged the Boston Cure Project's first initiative, the creation of a so-called cure map. So little is known about MS and there are so many possible contributing factors (genetic defects, toxic agents, viral or bacterial pathogens, trauma, nutritional imbalance) that what's needed is some way of plotting the landscape, seeing what's already filled in, what's yet to be explored, and where the obstacles are on the road to a cure. What's astonishing is that such a map didn't already exist. To Mellor, this is Management 101.

Next, he set about establishing a tissue bank, a pool of common tissue samples available to researchers from various disciplines, exploring various angles. All of Mellor's previous startups involved computer networks--building them, testing them, configuring them. The tissue bank promotes a highly effective network no different in Mellor's thinking from Midnight Networks. "We're not proposing anything visionary," he says. "It just makes sense. Because this is how people do work."

The Boston Cure Project may one day have a network of chapters all over the country. Today, though, it operates out of a single office in Waltham, Mass., in an office park otherwise populated by the kinds of tech companies that used to be Mellor's universe. It has a paid staff of four; Mellor's most recent hire was a full-time development director. As executive director, Mellor pays himself a salary of $35,000 ("I'm making what I made when I graduated from college"); he's hoping to bump that up to $40,000 by the end of the year. "My panic level is decreasing with time," he says, "which is what I want. I'm hoping that within a couple of years I'll be able to have a life again. That's about how long it took at the other companies."

Which raises the question: If Mellor has such confidence in his approach, why not set up a for-profit company, raise some real money from VCs (instead of the nickels and dimes he's raised so far from golf tournaments and scavenger hunts), hire some crack researchers, and look to make a killing on the cure? "With something like this you want to align your mission with your reward structure," Mellor explains. "And in a for-profit environment, your reward is profit. Your mission may be initially aligned with that, but as you're working along, you have to follow the reward thing. In fact you're legally bound to watch out for the shareholders' profit. So you could be working on something for MS and stumble upon a cure for Parkinson's disease and would have to turn into a Parkinson's company." And then where would Mellor be? He'd be rich, but he'd still have MS.

On a hot night in August, I joined Mellor at a pub in Waltham for a Boston Cure Project event billed as an MS Social. My wife has MS--she was diagnosed 18 months ago--and I had invited her to come. As soon as I walked into the bar, I was glad she'd had other plans. It was the wheelchairs--too many people in wheelchairs. I'm not sure she's ready for that; I'm not sure I am either.

Mellor was working the room, dressed as always in a Boston Cure Project T-shirt. ("He needs a new wardrobe," says his wife, Debbie, sighing.) At first glance, he appeared entirely healthy, bouncing from table to table, handing out business cards and name tags, making connections. But since my wife's diagnosis, my eye has grown sharper. I noticed his heavy feet, his plodding gait. I asked Debbie about it later, and she confirmed what I suspected: The numbness had risen now to the middle of his chest. She said he was gearing up for another round of steroid treatments, which can alleviate severe symptoms but often with severe side effects. Mellor has experienced psychotic episodes while on steroids.

All of which serves only to reinforce his motive. "I wouldn't do this if I didn't have the disease," he says flatly. He once went so far as to suggest that if it turns out that MS is not one disease but several, and by his efforts he's able to cure his particular version but not the others, he might abandon Boston Cure Project. Mellor is sick. He's desperate for a cure. For him, that's what it's all about.

But here's the irony. The odds that Mellor's efforts will lead him to a cure for MS in time to save himself are slim indeed. Or, put another way, the only goal he admits to is one he's likely never to achieve. Yet the goal he denies--that of helping others--is a different story. One day MS will probably be cured, and Mellor's efforts will have played a part. Smart as he is, he has to know that.