Microsoft has announced plans to return about $75 billion to shareholders over the next four years, including a special, one-time dividend of $3 per share.

The company's board has also approved a quarterly dividend of $0.08 per share and a plan to buy back up to $30 billion of Microsoft stock between now and 2008.

The announcement ends growing speculation as to how and when Microsoft would begin distributing the vast fortune that it has amassed, which amounted to $56.4 billion in cash and short-term investments at the end of its most recent quarter. The software maker had been expected to reveal the plan at a meeting for financial analysts next week.

Microsoft said the move was motivated in part by confidence in its ability to increase revenue and profit in the coming years through innovation and new products. But the timing was clearly also driven by its success in settling numerous lawsuits against the company, reducing the likelihood of substantial litigation costs in the future.

"We think that we've put many of our legal issues in the rear-view mirror, so to speak, which affords us this opportunity to move forward with the cash management plan that we announced today," said Microsoft CEO Steve Ballmer.

Bill Gates, Microsoft's chairman and chief software architect, called the move "a pretty exciting milestone".

In a separate statement on Tuesday, Gates said he would donate his proceeds from the one-time stock dividend, worth about $3 billion, to the Bill & Melinda Gates Foundation.