Microsoft has started offering the free Windows 10 upgrade it promised for machines running Windows 7, 8 and 8.1. Meanwhile, reports are saying the actual download or release date of the operating system will likely be July 29.

The reservation offer was first spotted May 31, a blog by Venture Beat reported. A pop-up message from Microsoft briefly provided details of the update process -- how it works and the system requirements. The notification, however, did not mention when the rollout would begin.

KB 3035583

The invite to reserve, as expected, is for the Windows versions mentioned above, but the blog report also noted personal computers that get the upgrade prompt have one thing in common -- they recently installed KB 3035583. This update triggers the whole procedure, in which users can reserve a download spot once Windows 10 is ready to hit the street.

The reservation can be canceled if users decide against test driving the new OS early on. But for early adopters, there are simple steps: reserve, install, enjoy. The first one merely requires that a user grab the offer.

Microsoft will follow up later with a second notification that will say the download is ready and can be started at any time. Users have the option to upgrade immediately or do it at a later, more convenient time. It should be noted the offer expires after 12 months.

The last stage is actual installation with Microsoft specifying PCs lined up for the jump must have at least 3GB of unused storage space and a broadband Internet connection for download. The software giant reiterated too the upgrade is free and not a trial.

Launch Date

What’s missing on the notice is the exact rollout time but the Verge reported Windows 10 has been programmed to arrive July 29. The information, according to the tech blog site, came from sources it described as “familiar with Microsoft's plans.”

At the moment, Windows 10 is approaching the code completion stage, at which point the OS is locked and its features finalized. No major changes will follow except to fix identified bugs in the ensuing testing phases. Then the Windows 10 RTM, or release to manufacturing, build will come next. The Verge said that is likely to happen the last week of June, setting the stage for the software’s commercial debut a month later.

The forecast appears in line with an earlier report indicating retail availability of Windows 10 Aug. 31.