Microsoft is celebrating its 30th birthday in an upbeat mood, promising to deliver twice the number of new products and services as it has during the past three years.

Speaking at the firm's annual meeting/birthday bash held at Safeco Field in Seattle, chairman Bill Gates spoke of Microsoft's achievements so far and the challenges ahead.

"As I think about the past 30 years, I'm most proud of our making 'big bets' on technologies like the graphical user interface or web services, and watching them grow into something people rely on every day," he said.

"And the long-term research we're doing today on some of computer science's toughest challenges, such as helping computers listen, speak, learn and understand, will lead to what I think will be the next wave of growth and innovation for our industry."

Life began in 1975 for Microsoft but its big break came when the firm licensed an operating system it had bought called QDOS (Quick and Dirty Operating System) to IBM in 1981, while retaining the rights to sell it itself.

IBM turned down an offer to buy a 10 per cent share in the company, which would be worth $27bn at today's prices.

In 1991 Microsoft ended its relationship with IBM and began to focus on Windows and Windows NT kernel development, later releasing Microsoft Office which soon became the leading office applications suite on the market.

Ten years later the firm was jolted into action by an internet start-up called Netscape, which had released the power of the internet to millions of new users with its web browser.

Microsoft responded by developing and bundling its own browser with Windows, effectively killing Netscape.

The action led to an antitrust probe, and the European Union continues to investigate Microsoft's activities.

Its recent sluggish share price, and accusations of bureaucracy and delays to the forthcoming Vista operating system, will inevitably take some of the shine off today's celebrations.

But Microsoft has grown from two employees in 1975 to 60,000 today and, with $40bn in cash reserves managed by a small army of investment analysts, the firm has problems that other corporations can only dream of.