Apple CEO Steve Jobs announced a successful end to the transition to Mac OS X at Macworld Expo San Francisco this month – and the company repeated the message during its first-quarter results call last night.

Apple chief financial officer Fred Anderson, while predicting lower Panther sales in Apple's second quarter, claimed that all of Apple's estimated 20 million installed base of Mac users should be technically able to upgrade to Mac OS X.

With Mac OS X users now approaching ten million, Anderson added that, if older Macs are included within the user base calculations, the actual number of Mac users is far higher. Mac OS X 10.3 Panther sales delivered $60 million in revenue in the quarter, Apple said.

Apple CEO Steve Jobs said: "We're kicking off 2004 with strong momentum, especially for Mac OS X, which is now used by almost 40 per cent of our installed base, iPod and the iTunes Music Store, which has a 70 per cent share of the legal music download market."

"This is the fastest OS transition on record," Jobs claimed during his keynote speech.