"Give it away, you'll enjoy it," Gates tells rich

Bill Gates, Microsoft founder and co-chairman of the Bill and Melinda Gates Foundation, attends a session at the World Economic Forum (WEF) in Davos January 30, 2009.

OSLO (Reuters Life!) - Microsoft founder Bill Gates said on Wednesday that billionaires ought to give away most of their wealth to charitable causes, and they would even find they enjoyed it.

Gates has given much of his wealth from Microsoft, the U.S. software giant that made him the world's richest man, to the Bill & Melinda Gates Foundation, a philanthropic powerhouse.

"I think all billionaires should give away the vast majority of their fortunes -- though I don't say they shouldn't leave anything to their kids," Gates told a gathering at Oslo's opera house.

"I think they would enjoy it, their kids would be better off, and the world would be better off," Gates said.

"I'm a great believer that great wealth should go from the richest to the poorest," he said, seated next to his wife Melinda who co-chairs the foundation.

Gates renewed his appeal to eradicate polio, saying the goal was well within reach, which would make it the second major communicable disease entirely wiped out after smallpox in the late 1970s.

"We have to get rid of polio because if we don't, it will spread back and we will have millions affected," he said.

Gates said his foundation's biggest success had been in the field of vaccination.

"Vaccination is the area where we have saved millions of lives, and there is more to be done."

Gates said it was a big disappointment that science had not produced a vaccine to prevent HIV/AIDS, but he said he was optimistic about some emerging prevention methods that could be used by women to stop infection before a vaccine is discovered.

Once one of those methods proved to work, he said, the foundation would work "to get it out there and dramatically decrease the number getting (the disease)."

"The holy grail for AIDS is to have a vaccine, which is something we are also working on," Melinda Gates said.

"It will probably be 10 to 15 years before we get that," Bill Gates said.

(Reporting by John Acher, editing by Paul Casciato)