Microsoft officially stopped selling retail copies of both Windows 7 and Windows 8 on October 31.
The date to stop selling the software was set some time ago and should help Microsoft move people on to more recent versions of its operating system.
Separately, statistics suggest people are finally moving away from some very old versions of Windows.
The next version of Windows, called Windows 10, is due to be released in late 2015.
From October 31, consumers could no longer buy copies of the Home Basic, Home Premium and Ultimate versions of Windows 7. Now, Windows 8 is also no longer available. The change affects both copies bought in shops or loaded on PCs and laptops.
The current version of Windows, 8.1, will be the default version offered on PCs.
The change will take time to feed through into the market, as many PC makers have large stocks of older versions of Windows and will continue to sell PCs running the software.
Those keen to get a computer running Windows 7 will be able to “downgrade” from 8.1 to Windows 7 Professional but relatively few PC firms offer this option.
The original version of Windows 8 did not prove popular because it did away with some familiar elements of the desktop version of the operating system.
Windows 7 has been available since late 2009 and is still very popular among users. About 53% of Windows users are on the various editions of Version 7 of Windows. The more recently released Windows 8 has only grabbed a 6% market share and has already been surpassed by 8.1.
Separately, market analysis reveals that the numbers of people using the venerable Windows XP operating system has suddenly seen a sharp decline. Data from Netmarketshare suggests that in October this year its share dropped from almost 24% to just over 17%.