There are already twice as many punters running Windows Vista as using Macs worldwide. Microsoft's announcement of its 40 million-strong Vista install base coincides with the 100 day anniversary of the OS.

Microsoft supreme Bill Gates spoke to an audience at the Windows Hardware and Engineering Conference ( WinHEC ) in Los Angeles. He said that Vista is selling twice as fast as Windows XP did at the same stage.

Gates also couldn't resist a poke at Apple: "That says that in our first five weeks we've matched the entire installed base of any other provider of similar software". Apple's own website says there are "nearly 15 million active users" of Mac OS X. Though the actual number of Mac users is thought to be around the 20 million mark.

Since Vista was launched on 30 January, Microsoft says it has sold a staggering 400,000 new Vista installations for every day, both in store and sold on manufacturer's PCs.

More remarkable is that the most expensive version, Windows Vista Ultimate, has accounted for nearly 80 per cent of sales. The going has been tough in some territories, notably China, where few copies have reputedly been sold because of rampant piracy.

Read more about Vista's sale bonanza and the latest from WinHEC.