Microsoft CEO Steve Ballmer today said that the company had sold 4 million upgrades to Windows 8 since Friday, when the discounted deals kicked off.
"In just the last three days, we have sold 4 million Windows 8 upgrades," Ballmer said during his early minutes on stage at Microsoft's BUILD Conference Tuesday. "The level of embrace from enthusiasts is very, very high."
He later called the uptake "stunning."
Ballmer's number did not take into account sales to enterprises, many of which have volume license agreements that automatically let them upgrade to the newest Windows.
Microsoft officially launched Windows 8 on Oct. 26, when it first let customers download the $39.99 upgrade to Windows 8 Pro, and began fulfilling the $14.99 deal for those who purchased a new Windows 7 PC starting June 2.
On Friday, retailers also started selling boxed copies of the Windows 8 Pro upgrade on DVD for $69.99.
While Ballmer trumpeted the 4 million upgrade figure -- which would be mostly downloads, as retail sales data would be difficult to collect so quickly -- there's no way to compare the number with earlier Windows' roll-outs.
In late 2009, after Microsoft rolled out Windows 7, the company was cagey about sales for months, and never publicly revealed upgrade numbers.
Two weeks after Windows 7's debut, a Microsoft executive said it was too early to characterize sales, and Ballmer merely described the response as "positive."
At the end of this month, usage statistics from the likes of Net Applications should show an increase in Windows 8's share, but unless it surges dramatically, it will remain below the bar set by Windows 7 in late 2009. Before launch, Windows 8 adoption -- via a series of previews and the availability of an RTM, or "release to manufacturing" build -- was five times smaller than Windows 7 during the same period prior to its launch.
See more Computerworld Windows 8 launch coverage including news, reviews and blogs.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is email@example.com.