NetMarketShare shows Windows 10 going from 40.30 percent to 43.62 percent, a big gain of 3.32 percentage points. Windows 7 fell 1.9 percent, to give it 36.51 percent, down from 38.41 percent in February.

 Overall the ageing OS has lost 6.93 percentage points in a year, while Windows 10 has grown by 9.79 percentage points.

There is currently a gap of 7.11 percentage points between Windows 10 and Windows 7 which is probably going to be permanent.   Windows 8.1 declined 0.24 percentage points. It now has a 4.13 percent share.

Windows 7 is powering a lot of really ancient gear which its owners do not want to upgrade. It is expected that as this hardware dies, or catches fire, or otherwise goes to silicon heaven, Windows 7 will disappear. Still, existing on more than a third of machines shows how much of vulnerability there is in IT infrastructure. Windows 7 is not being upgraded and makes a soft target for hackers.