AS BILL Gates departs from Microsoft's full-time payroll, chat rooms, message boards, blogs and news sites have filled to overflowing with debate about his place in history: will the human icon of the personal computing era be remembered in years to come as a visionary, or as a corporate villain?

Or perhaps Gates' business exploits will be subsumed in history by the main occupation he takes up tomorrow as a so-called "super philanthropist". Giving away billions through his eponymous foundation to eradicate disease and poverty would – if even partially successful – rival his monumental role in shaping the PC industry as created by Microsoft and its ubiquitous Windows products.

Amid this speculation, a more apposite consideration for the roughly 78,000 people working for Microsoft around the globe is the legacy Gates has bequeathed to the company he helped to set up 33 years ago. The 900lb gorilla of packaged software is facing significant threats from younger rivals born of the internet, and it remains unclear whether Gates' successors can fend off the challenge.

Wary of unsettling investors or employees, Gates has disengaged from Microsoft's day-to-day operations at a slow and measured pace. His plan to give up his full-time role as chairman on Friday was announced two years ago. That followed his decision six years earlier to hand over the chief executive's seat to Steve Ballmer, a long-time friend and Microsoft associate.

Ballmer is known as a sales and marketing guy, and the gregarious chief executive admits openly that he's no technology expert, unlike his programming-savvy predecessor with a calculator in his head.

However, many analysts believe that technical leadership is exactly what Microsoft needs in the current climate. They point out that it's been nearly a decade since the company came up with a blockbuster new product, while rivals such as Google and Apple have cornered new markets.

To be fair, the origins of much of Microsoft's current shortcomings can be traced back to when Gates had a firmer hand on daily operations. However, Ballmer's efforts to turn back the tide have yet to bear fruit, while some – such as his plan for taking over Yahoo – have backfired.

Microsoft's unsolicited five-month courtship of Yahoo was meant to add much-needed online advertising and web services to its armoury for tackling the Google juggernaut. Instead, Yahoo rejected a final offer of $33 per share, opting to sign a lucrative advertising partnership with Google.

Because of their combined share of the US online ad market, Google and Yahoo have voluntarily delayed implementing that agreement while it is reviewed by the Department of Justice. Meanwhile, Yahoo is fending off efforts by rebel investors to replace the current board of directors, led by co-founder and chief executive Jerry Yang, with a slate of executives who would revive talks with Microsoft.

Ballmer believes it's essential that Microsoft gets it right with its online ad business, and, as such, he and his team are believed to be still pondering their options with Yahoo. In effect, they are grappling with the consequences of a rare lapse by Gates. The renowned visionary was gazing in the wrong direction when Tim Berners-Lee built the first browser and server for the web in 1991, and although Gates reportedly obsessed about the growth of the internet in the early 1990s, he was unable to quickly turn what had become a monolithic organisation into the correct direction.

Microsoft belatedly started flooding the market with new online services under the MSN umbrella in 1995, just as the first browser war between Internet Explorer and Netscape Navigator was heating up. In the summer of that year, Microsoft executives allegedly visited the Netscape campus with proposals to divide up the browser market. Microsoft has always denied the incident, even though it had long been accused of systematic anti-competitive behaviour.

Critics say Gates built much of the Microsoft empire by adopting software features and code from other companies. Officially termed "embrace and extend" by the company, some Microsoft employees cynically referred to it as "swipe and hype".

This remains unproven, but Gates faced the biggest test of his business career when more than 20 states in the US joined the federal government to launch an antitrust trial against Microsoft in 1998. The suit threatened a break-up of Microsoft, and Gates was convinced the government was out to "destroy" his company.

A break-up was eventually ordered in 2000, but Gates ultimately prevailed when that decision was rescinded a year later in favour of concessions by Microsoft to change its business practices. Microsoft would have less success three years later when the European Union accused it of abusing the dominant position of its Windows operating system, resulting in changes to its Windows XP platform and fines of ?497m.

While many cast Gates in the role of a modern day robber baron, others point out that his company has created enormous benefits for both individuals and the corporate world.

George Colony, chief executive of Forrester Research, recently described Gates as "one of the greatest monopolists in American history". By establishing Windows and Office as dominant technologies, Gates effectively enforced the standardisation of systems.

"Because of him, we take it for granted that you can easily share world processing files, spreadsheets and other documents," Colony said.

As Gates sheds the role of monopolist for that of philanthropist, it could be that he will ultimately go down in history as one of the greatest charitable figures of the 21st century. He leaves Microsoft at the relatively fresh age of 52, and could conceivably spend as much time giving away his fortune as he did in making it.

His stated aim to give away the bulk of his estimated $66bn in personal wealth has inevitably drawn comparisons with Andrew Carnegie, the cut-throat steel magnate who ruthlessly built his empire in the latter part of the 19th century, then gave nearly everything away to charitable causes.

Carnegie spent most of his money on libraries and other institutes of learning and research. The aim of the Bill & Melinda Gates Foundation is to improve health care and reduce poverty in some of the most deprived countries around the world, a far more formidable and elusive goal than constructing buildings.

It remains to be seen whether the image of Gates as a force for good will ultimately prevail. For millions of sick and starving people, the hope will be that his past pre-eminence in an industry he created translates into similar dominance over some of the world's most pernicious diseases.