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29 July 2015 Last updated at 05:00 BST
Microsoft is rolling out access to the latest version of its operating system in waves, to make sure everything runs smoothly.
The first people will be notified that an update is available on 29 July, while everyone else will have to wait.
The BBC's technology correspondent Rory Cellan-Jones was given a crash course in Windows 10 by product manager Ian Moulster.
He showed Rory some of the operating system's new features, including its voice controlled assistant Cortana.
Find out more about Windows 10
The first early adopters will be able to get their hands on Windows 10 from Wednesday.