The day has come, in that Valve, the company behind Steam, has announced that it will end support for some versions of Windows, which despite being old, still have thousands of active users who will no longer be able to play their favorite titles from the next 1 January 2019.
So has announced the company will leave the support of Windows XP and Windows Vista, that is to say, as you will not be able to run Steam on computers with these versions of Windows.
The reason is justified, in the first place because not even Microsoft itself supports these versions of Windows, so that they do not receive updates or security patches, that is to say, are insecure.
On the other hand, Valve has mentioned that Steam uses Google Chrome as the internal browser, and this browser has no longer support for Windows XP and Windows Vista, so Valve is putting at risk the safety and experience of their users who use these versions of Windows.
From 1 January 2019, only those who use Windows 7. Windows 8 / 8.1 or Windows 10 will be able to use Steam, the others will have to look for a new computer, or upgrade your machine to at least Windows 7.
As has been reported by the company itself, only 0.22% of users of Steam use Windows XP 32-bit, whereas neither Windows Vista nor Windows XP 64 bit appear in your list. However, Valve usually does not publish the figures of total users of Steam, except by the peaks of users connected simultaneously all over the world, being in average of 15 million, which means that at least about 33 thousand people might be affected by this decision.