Bill Gates attended to a bit of unfinished business yesterday.

Gates, who dropped out of Harvard in his junior year before co-founding Microsoft and going on to become the world's richest person, stopped off at his former stomping grounds to collect an honorary law degree.

"We recognise the most illustrious member of the Harvard College class of 1977 never to have graduated from Harvard," said Harvard University provost Steven Hyman.

"While his classmates, including his friend Steve Ballmer, were busy cramming for mid-terms, he was planning for a revolution, the rise of the personal computer," Mr Hyman said. "It seems high time that his alma mater hand over the diploma." Mr Ballmer is now Microsoft's chief executive.

During Mr Hyman's comments, Mr Gates (51) smiled and nodded to the applauding graduates. He was scheduled to address them later.

The lack of a degree didn't slow Mr Gates's rise to the top echelons of business. In 1980, Gates and his colleagues at Microsoft were canny enough to negotiate an agreement with IBM that gave the start-up software company the right to license its operating system for a new generation of PCs to other manufacturers.

That arrangement ultimately turned the computer business on its ear, shifting power from hardware manufacturers to software programmers. Today, hundreds of companies manufacture hundreds of thousands of brand-name personal computers each year, but more than 90 per cent of those machines use Microsoft's Windows operating system.

At Harvard, Mr Gates lived down the hall from Mr Ballmer, who stayed on to graduate after Mr Gates dropped out to focus his energies on Microsoft, which he founded in 1975 with childhood friend Paul Allen. Mr Ballmer joined Microsoft in 1980.

Microsoft went public in 1986 and by the next year the company's soaring share prices had made then 31-year-old Mr Gates the world's youngest self-made billionaire.