Update: Microsoft has told Bloomberg's Dina Bass that Yusuf Mehdi was mistaken when he said that OEMs would not have Windows 10 hardware on store shelves in time for the July 29 launch. The software firm says that Lenovo, Dell, HP, and Acer should all have systems available on the day of Windows 10's release.

Original article: Windows 10's July 29 release date is looming. The OEMs we've spoken to in the past few months have all been confident that they'll have at least some hardware with Windows 10 preinstalled available to buy on launch day.

It now looks as if those plans have been derailed. Bloomberg reports that Yusuf Mehdi, Microsoft vice president of Windows and device marketing, has said that Windows 10 hardware will be available "very soon after" July 29 but not on the day.

The problem is that Windows 10 still hasn't had its release to manufacturing (RTM) version yet. It was initially expected that the RTM would be built last week, but it hasn't been. Currently the rumor mill is speculating that Wednesday will be the day. Either way, it seems there won't be enough time for the OEMs to test the build, install it to newly built systems, and get those systems delivered to retailers' shelves in time for July 29. The new Windows 10 release schedule was already significantly compressed—in previous versions there were usually a few months between RTM and retail availability—and as such has a lot less slack to cope with these delays.

Just how soon the hardware will be available will depend on when a build is blessed with RTM status. Even if everything had gone according to plan, OEMs weren't expecting to have Windows 10 versions of their full range available on day one; it will take some weeks or months before every machine is available with the new operating system.

In spite of the hardware shortage, Microsoft is planning a series of launch events for the new operating system with Windows fans as the focus. There will be "hands-on opportunities, experiential demos, entertainment, and opportunities to meet the Windows team" in Sydney, Tokyo, Singapore, Beijing, New Delhi, Dubai, Nairobi, Berlin, Johannesburg, Madrid, London, São Paulo, and New York City.

Further Reading Microsoft clarification kinda clears up free Windows 10 license confusion

Unlike prior versions of Windows, Microsoft is anticipating, and hoping, for a substantial volume of upgrade users. In practice, most Windows users stick with the operating system that comes preinstalled on their PCs. The fact that upgrading to a new version of Windows has historically cost money reinforced this trend. With Windows 10 and its one-year free upgrade promotion, Microsoft is counting on a significant volume of users making the leap from Windows 7, Windows 8, and Windows 8.1. To achieve its goal of one billion Windows 10 devices within two years, the company will have to make significant inroads into the large non-tech-savvy Windows userbase; a demographic that is not predisposed to performing operating system upgrades.

To help stimulate and support this, the company is partnering with a number of retailers (and its own stores) to help users upgrade. Retailers participating in this scheme include Best Buy, Bic Camera, Croma, Currys/PC World, Elkjøp, Jarrir, Incredible Connection, Media Markt, Staples, Wal-Mart, Yamada, and Yodobashi, and they'll provide support for the upgrade, assist in data migration to new PCs, and let people try the operating system for themselves. The new operating system will also be promoted in advertising starting on July 20 in the US and July 29 in the rest of the world.

For those not upgrading in-store, availability of the upgrade will be staggered. Windows Insiders who have been using the preview releases of the operating system should be the first to get the RTM build, and new PC buyers will also be prioritized. Windows 7 and 8 users who will be upgrading through Windows Update will see a somewhat slower rollout, giving Microsoft the chance to gauge how successful upgrades are and detect any last-minute bugs should they arise.