Windows users are transitioning to Windows 11 at a slower rate than the upgrade to Windows 10. Microsoft’s 10-year-old operating system, which just hit the end of support phase, is still proving popular among consumers and businesses. Dell revealed this week that around 500 million machines are capable of upgrading to Windows 11, but are sticking with Windows 10 instead.

“We have about 500 million of them capable of running Windows 11 that haven’t been upgraded,” said Dell COO Jeffrey Clarke on a Q3 earnings call earlier this week, referring to the overall PC market, not just Dell’s slice of machines. “And we have another 500 million that are four years old that can’t run Windows 11.” He sees this as an opportunity to guide customers towards the latest Windows 11 machines and AI PCs, but warns that the PC market is going to be relatively flat next year.

It’s the first time we’ve heard that as many as 500 million machines are holding off upgrading to Windows 11, and that a similar amount simply can’t. Microsoft tightened its hardware requirements for Windows 11, leaving behind millions of PCs that were sold over the past decade.

Dell’s Windows 11 upgrade numbers come just a week after Windows chief Pavan Davuluri said that “nearly a billion people rely on Windows 11.” It’s not clear what rely means here, as Microsoft has typically provided monthly device numbers in the past.