Microsoft’s Bill Gates will leave his day-to-day duties at Microsoft in July 2008 to pursue his passion to fulfill the mission of helping less fortunate people throughout the world through the foundation he started with his wife.

Gates, the founder, chairman, and chief software architect, plans to remain as chairman of the company for the foreseeable future, he said during a press conference after Thursday’s final bell on Wall Street.

“I believe with great wealth comes great responsibility,” he said. “Responsibility to give back to society… responsibility to see those resources put to work to help those most in need.” As of last year, Gates and his wife had endowed the Bill & Melinda Gates Foundation with more than $28.8 billion to support philanthropic initiatives in the areas of global health and learning.

During the two-year transition away from Microsoft, Gates said he would continue to work as hard as ever. “This was a hard decision for me, I am lucky to have two passions,” he said.

Ray Ozzie, the CTO for Microsoft, will immediately assume the title of chief software architect and will work side-by-side with Gates over the next two years.

“I’ve worked with Ray for over 20 years and his vision has led to some of the most important developments in our industry,” said Gates.

Craig Mundie, another CTO for the company, also will immediately take the title of chief research and strategy officer and work with Gates to take over his responsibility for Microsoft’s research and incubation efforts. Mundie also will partner with general counsel Brad Smith to guide Microsoft’s intellectual property and technology policy efforts.

CEO Steve Ballmer said the transition would not cause a ripple in the company.

“We plan to make a smooth and orderly transition to a new set of technical leaders without missing a beat.” He also said Gates’s announcement was an emotional day for him given their close personal relationship, but Ballmer predicted that his friend would go on to become the greatest philanthropist of all time.

Gates said Microsoft would continue to thrive into the future, mostly based on the talent and commitment at the company.

“The world has focused a disproportionate amount of attention on me,” said Gates. “In reality, Microsoft has always had a strong depth and breath of technical talents.” Indeed, experts say it won’t be a talent hit that Microsoft takes but more of a visibility hit.