It has been 25 years since the potential market failure of a Microsoft operating system carried serious consequences outside the corporation's own campus.
MS-DOS and Windows versions have failed to gain traction before and even been publicly lampooned.
But in that quarter-century, Microsoft's dominance of the desktop has kept the platform afloat, even when consumers and businesses stalwartly refused to upgrade.
Today, the word "dominance" doesn't really apply to Windows, and especially not to Microsoft.
Windows 8 was a spectacular flop, sunk to a large degree by the start screen. If Windows 10 performs no better, there are two views of the consequences.
One is that the Windows platform is now vulnerable to obsolescence. So, like a Prime Minister facing a multiparty no-confidence vote, a Windows 10 failure would force Microsoft to make an airtight case for why a Windows operating system must continue to be produced.
Yes, Windows versions have failed before, without Taps being played or world economies crumbling. It's not because Windows hasn't mattered that much.
As with mediocre leadership or poor cable service, people will put up with what they have in the absence of a better alternative.
But if Windows 10 doesn't catch on, device makers may move away from PCs altogether. The products they make, using other native OSes or even virtual desktops, may look less and less like laptops and not much different from tablets.
Some analysts have an alternative view: It's Windows 7, not 8, that has the lion's share of the operating system's installed base. If Windows 10 performs no better than Windows 8 in the consumer, small business, and enterprise markets, Windows 7 will simply linger on.
"Windows 7 offers strong competition to any new desktop OS," said Al Hilwa, IDC's program director for software development research, in an email interview.
"But as long the new environment is sufficiently familiar to both users and developers, the replacement rate for PCs will ensure a continued switch, and some success."