Gates, whose estimated net worth climbed US$6 billion in 2006 to $56 billion, was joined in the top 25 by technology heavyweights Larry Ellison, chairman of Oracle Corp., 11th place, $21.5 billion; Paul Allen, formerly of Microsoft, 19th, $18 billion; and Azim Premji, chairman of India's technology services company Wipro Technologies, 21st, $17.1 billion.

Microsoft's CEO Steve Ballmer, however, watched his ranking drop from 24 in 2005 to 31 even as his net worth climbed to $15 billion from $13.6 billion.

Michael Dell, the back-again CEO of Dell, placed 30th last year with $15.8 billion, a drop in both ranking (12) and worth ($17.1 billion) from 2005, mirroring the decline of the company he founded.

Other notable names on the list include Apple Inc.'s CEO Steve Jobs, 132, $5.7 billion; Google Inc.'s co-founders Sergey Brin, 26, $16.6 billion, and Larry Page 26, $16.6 billion, and Google's chairman and CEO Eric Schmidt, 116, $6.2 billion; Amazon.com Inc.'s CEO Jeff Bezos, 188, $4.4 billion; Yahoo Inc.'s co-founder Jerry Yang, 432, $2.2 billion; Gordon Moore, co-founder of Intel Corp., 243, $3.6 billion; and eBay Inc.'s founder Pierre Omidyar 76, $8.8 billion.

Among former technology billionaires who didn't make the cut in the 2007 ranking was Canadian Calvin Ayre, founder of the online gaming company Bodog Entertainment Group. In 2005, Ayre's net worth was estimated at $1 billion, but the U.S. government's on Web gambling shoved him off the list.