The number of people using Windows XP has continued its slow decline - but it appears to be Windows 7 winning them over, not Windows 8 or 8.1.
The latest market share stats from Net Applications show Windows 8.1 and 8 down very slightly from the month before, but essentially flat.
XP slid below 25 percent or the first time, down from 37 percent a year ago, while Windows 7 continues to post growth, up to 51 percent from 44 percent last year - despite the launch of the new OS.
The stalled take-up highlights the troubles Microsoft is having flipping new users to the new version of Windows, with rumours suggesting the next major update will be Windows 9 so the company can leave behind the tarnished "8" brand.
Combined, Windows 8 and 8.1 have reached a 12.48 percent market share - less than half of Windows 7's 29.6 percent share the same number of months after launch.
Net Applications' data is based on web browsing, not actual sales figures. Microsoft said earlier this year that 200 million Windows 8 licenses, which wasn't much less than Windows 7 at about the same point.
However, Microsoft isn't helped by slow PC sales: most Windows upgrades happen when consumers buy new hardware, and with flat sales, that's making it even harder for Windows 8/8.1 to make a mark.