Microsoft Windows 10 is having some early success as it is being reported that 18.5 million computers have already updated to the latest operating system, TechRadar reports.

The 18.5 million number comes from news site NeoWin and it corrects the earlier inflated numbers of over 20 million installs. With 67 million machines registered to receive the update, this number should continue to grow.

Microsoft reported that 14 million installations of Windows 10 were performed on the first day that operating system was available to the public. During the peak download times, Windows 10 was being installed on 1,500 machines a second.

With such a high level of downloads, there have been errors and bugs in Windows 10. These bugs and errors are expected when a big update like this is released to so many computers, especially at no cost.

Windows 7 and 8.1 users have a full year to decide if they want to upgrade to Windows 10. During the year-long period, Windows 10 will remain a free upgrade for these users. After that, it will have to be purchased for the full retail price.

Word-of-mouth advertising is one way that Microsoft can count on more consumers upgrading their computers to Windows 10. Those who have already upgraded will definitely be sharing their experiences with the new operating system to their friends and family. If they are delighted with it, they could convince these undecided computer owners to upgrade to the brand new free operating system.

Microsoft's next big project is another big operating system release, this time Windows 10 for Mobile. That phone-based operating system is expected in the upcoming months. The new mobile operating system will continue to try to compete with Apple's iOS and Google's Android operating systems.

Windows 7 and 8.1 users are encouraged to reserve their update to Windows 10. When their update is ready, they will be notified and prompted to begin the installation process.