Within the first 24 hours of its release, Microsoft recorded 14 million devices running Windows 10.
The company said in a blog post on Thursday that they are working around the clock to continue the rollout process of the upgrade, prioritising those that had reserved the upgrade previously.
The rollout began on July 29 as a free upgrade to every qualified device running Windows 7 or Windows 8.1 for 365 days.
On the day of release, Akamai reported that internet traffic was 35 percent higher than normal on July 29, with the upgrade being 3.5GB in size.
With the target pinned at 1 billion devices running its latest operating system, Microsoft said that the rollout has been split into phases to "ensure that everyone has a great upgrade experience".
"We are grateful for your excitement and enthusiasm and we appreciate your patience over the days and weeks ahead as we carefully roll out Windows 10 in phases to all of you that have reserved," the company said.
Microsoft said that users who reserved a Windows 10 upgrade will be notified via a PC alert that their machine is ready and that the update has been downloaded.
With its new operating system, Microsoft has changed the way some of its apps behave. Card game Solitaire will cost players $1.49 a month -- $9.99 per year -- to remove the adds on the game and upgrade to its premium version.
Windows 10 is also now available on new hardware.