The Redmond, Wash. company also announced it will extinguish the Insider program for Windows 10 Enterprise, which some corporate customers have used to test the new OS since 2014.
Today marked the official launch of Windows 10 as the company began triggering upgrade notices on devices whose owners had previously "reserved" a copy using an app Microsoft pushed onto Windows 7 and 8.1 systems last month.
The simultaneous release of .iso files -- downloadable disk images -- gives customers another way to install Windows 10. Using an .iso file, users can "clean install" Windows 10 -- starting from scratch in other words -- and activate the OS using a valid Windows 7 or Windows 8 product key. Alternately, the .iso can be used to do an in-place upgrade of an eligible device.
Those .iso files and a media creation tool -- the latter assists in making a bootable USB flash drive or DVD -- can be found on Microsoft's website. Both 32- and 64-bit versions of the OS are available, as are versions in more than 30 languages.
Along with the disk images, which Microsoft had promised prior, the company also released an evaluation edition of Windows 10 Enterprise, the SKU (stock-keeping unit) widely used in large organizations. Enterprise SKUs are available only to customers who have volume-licensing agreements and carry Software Assurance annuity contracts.
The Windows 10 Enterprise evaluation edition expires after 90 days, but during the three-month stretch is fully functional.
In a different turn, Microsoft will also abandon the Insider preview for Windows 10 Enterprise that's been available since last fall. The program -- a subset of the Windows Insider beta deal which will continue -- will go dark Oct. 1, when the Enterprise preview builds expire.
"If you are running the [Windows 10 Enterprise] Preview, we will send you notifications beginning on September 15, 2015, to remind you that it is time to upgrade your PC to a newer version," Microsoft said in a long FAQ about the 90-day evaluation edition. "After October 1, a clean installation of Windows 10, the Windows 10 Enterprise 90-day Evaluation, or your former operating system will be required; and you will need to reinstall all of your programs and data."
Corporate customers may still participate in the Insider program after Oct. 1, but all on that "branch," or track, will get their builds from the same source.
Microsoft has encouraged IT professionals to keep atop upcoming changes in Windows 10 by subscribing to the Insider release branch. The disappearance of the Enterprise Insider program may be Microsoft's way of ensuring that no one tries to run an unpaid version of the Enterprise SKU, since consumers, enthusiasts and small business employees who used an .iso to do a clean install up until this month will be allowed to run the beta builds even if they didn't have a legitimate license backing up the preview.
Users can retrieve the Windows 10 Enterprise evaluation from Microsoft's website. A Microsoft Account is required, as is registration.