Thread:Deathstalker666/@comment-26005008-20160407215658/@comment-1496755-20160610061402

The internet was very limited in those days, so most people were stuck with whatever version they had ordered, unless they could get the patch (either directly or from a friend). Naturally, id Soft did not rely solely on patches - when new versions came out, they would discontinue the older one and start shipping the new one. I have seen both 1.1 and 1.2 disks, and there were also patches to upgrade to 1.2 or 1.666 (and beyond). Originally, you had to apply several patches and update step-by-step, but eventually they made cumulative patches that directly upgrade any version (from 1.1 to 1.8) to 1.9, and finally an additional patch that upgrades 1.9 to Ultimate Doom.

Doom II had a similar history, though it had two version that Doom 1 did not - 1.7 and 1.7a.

Windows 2000 is like a simplified version of XP, in many ways - it lacks the cooler visual themes and some of the functionality, but at its core it is pretty much the same (Win2000 was designated version 5.0, while XP was 5.1).