In between, Estridge not only helped create the personal computer, but he helped create an entire industry.

Estridge led the team that designed the first IBM PC, which quickly overtook the Apple computer in the marketplace. He also led the teams that first began selling them.

For a company used to selling very big, very expensive mainframes through its direct-sales force, selling small, relatively inexpensive PCs through retailers and resellers was almost an unheard of step.

Born in 1937, the native Floridian entered the University of Florida at Gainesville in 1955. During his college days, he met his future wife, Mary Ann, and the two married in 1958. He graduated in 1959 and went to work for IBM in the days when punch cards were all the rage in computing.

But even in a stodgy, corporate-minded place like IBM's Kingston, N.Y., site during the early 1960s, where Estridge worked on computer systems under the company's contract with the U.S. Department of Defense, glamour jobs found Estridge.

In 1964, Estridge was assigned by IBM to work with NASA on the nail-biting, historic Apollo moon missions.

Book and press accounts both quote Estridge about those days: "There was nothing like watching [astronaut Frank] Borman come from behind the far side of the moon for the first time. We knew to the tenth of a second when he would appear and that if it didn't happen then, he'd never come out," he recalled. "And there he was."

His assignment to develop and begin selling the personal computer--on the heels of Apple Computer Inc.'s success--was not an easy one in IBM's terms.

While the computer giant was notorious for three- to five-year product cycles, Estridge, who with gray hair and a 6-foot, 4-inch frame had been given the moniker of Cary Grant of the PC industry, and his barebones team of 14 developers were given a year to come up with a PC.

In the summer of 1980, Estridge was given the leeway to do whatever it took to get the job done. For Estridge, that meant goring some of IBM's sacred cows.

For one thing, the PC was built with cheap, easy-to-find components from outside vendors. That bucked IBM's history of building products--from soup-to-nuts--from all IBM equipment.

The next was Estridge's decision to put Microsoft Corp.'s DOS on all of its machines. To do that, he had to trust the company's co-founders, Bill Gates and Paul Allen, a duo that others at IBM greatly disdained.

As Gates would remember later in forums such as an interview with the Smithsonian Institution, working with Estridge's group was not the same as working with traditional IBM.

"They had actually a fairly small team," Gates recalled years later. "So, in a sense, we were working with IBM, but in a sense we were working with a small team."

When the Boca Raton, Fla.-based team was turned over to Estridge, "It was Don who I worked with a lot, and the people who were working for Don," Gates remembered. "It was a very close partnership at that level because they were a little naive and very open-minded."

IBM soon raised Estridge's unit to division status, calling it the Entry Level Systems Division, basing it in Boca Raton and making Estridge its first president.

And even after developing the PC in IBM's skeleton labs in Boca Raton, Estridge still had to find a way to sell them. And this, according to Sam Palmisano, currently head of the PC Co., Somers, N.Y., was the challenge.

"What he had to do was come up with a different business model. That's what he had to do. He had to create a different business model to get it going," Palmisano says, "because the business model we had at the time would have been difficult to get to the rate and pace required in this industry. And Don was able to do that."

Because IBM could not have the same market strategy with the PC that it had with Selectric typewriters or its mainframes, Estridge and the Entry Level Systems Division struck up relationships with dealers. Estridge believed in third-party dealers as a key to the company's PC sales.

In September 1982, Estridge's unit created its Dealer Advisory Council to advise it on products and a go-to-market strategy.

"When the council spoke, Estridge listened," wrote James Chopsky and Ted Leonsis in their book on the IBM PC's creation, "Blue Magic."

He listened to good advice and bad. Most of the dealers had only positive remarks about one of Estridge's biggest blunders, the PCjr, which bombed in the marketplace. But the seeds for IBM's cooperation with third-party dealers in the reseller channel emerged under Estridge's watchful eye.

And so what if it ruffled the feathers of others at IBM?

"Don had become so popular that he was the only one I knew that, when the chairman called, he didn't have to pick up," recalls Sam Albert, a longtime IBMer who worked with Estridge and is now an industry consultant and a director of the Computer Museum in Boston.

But others at IBM had become jealous or unforgiving of Estridge's shun-the-corporate-norm style. After making the Entry Systems unit a full-fledged division, Estridge had numbers to make just like any other division head.

He did, though. Within four years of starting the unit from the ground up, Estridge built IBM's PC business into a $4.5-billion-a-year business. From the original 14 employees, the unit had 10,000 by the time he left.

Another convention that Estridge broke with in getting the PC off the ground was to, essentially, make the specifications in the box available to the world, so that a generation of would-be Gateses and Allens could write their own software applications to work inside the IBM box.

Thus, largely because of that decision by Estridge--never before considered in a company known for its proprietary technology--the computing world became divided largely into two camps: Apple and "IBM-compatible."

Some 15 years later, "IBM-compatible" essentially has come to dominate the desktop arena so much that it is rarely given a second thought.

And, years before current IBM Chairman and Chief Executive Louis Gerstner began to speak out on the need for the computer giant to "eat its own cooking"--i.e., use its own products--Estridge oversaw the Boca Raton unit's own implementation of the PC as its computing tool of choice even before the rest of the world began to adopt it.

In 1985, though, it was time for him to move on, and he left that unit to head up IBM's worldwide manufacturing operations.

While others, like Gates, have been able to enjoy the fruit of the seeds that Estridge planted, he was not.

On Aug. 2, 1985, Estridge and his wife boarded Delta Flight 191 from Fort Lauderdale to Dallas-Fort Worth--the first leg of their trip to Jackson Hole, Wyo., for a vacation. Estridge, who recently had left the IBM PC operation to take over the manufacturing operation, was readying to move from Boca Raton to IBM's Armonk, N.Y., headquarters.

The plane crashed short of the runway, killing the Estridges and five other IBMers. The Estridges left behind four grown daughters.

But Estridge's legacy lives on. When Palmisano unveiled IBM's new SystemCare business model earlier this year, he invoked Estridge's name as an innovator and standard-setter. "I think Don really understood the paradigm of personal computing in the business environment," Palmisano said.

And in 1991, to commemorate the 10th anniversary of the PC industry--which began largely as a result of Estridge's efforts--a huge party was held on a yacht that circled Manhattan. Aboard were many of the industry's elite, including Gates, Apple co-founder Steve Wozniak and several members of the original IBM team.

"At one point, there were several of us at the side of the boat, looking down into the river, reminiscing about what had happened over the past 10 years," Albert recalls. "Everyone was there except Don."