This is not what most of you want to hear about, but I am using right now and have for years "Windows XP".
For a browser I am using and have also for many years "Firefox" the version is a little old 37.0.2.
Both, Windows XP and Firefox work just fine, they are very responsive (quick to react) and fast, sometimes I have 15 to maybe 20 or more web pages open at the same time, of course, when I have so many web pages open at the same time Firefox slows down and maybe mostly if they are video pages from "YouTube", but I think that most of the time if I only have about 10 Web pages or fewer open at the same time there is no slow down at all or very little.
My Firefox browser is most of the time very responsive and fast, only sometimes but not very often there are "scripts" problems and slowdowns on some few Web pages, with Firefox the biggest source of problems have been "Adobe Flash Player" always telling me that my installed version is not secure and outdated and don't like to "Auto-Update" any software and "Adobe Flash Player" seems to UpGrade way too often for my taste.
As to Windows XP or at least the Win XP that I have, it is also very responsive and very fast most of the time, of course, there are some software programs that are slow and or very slow, but those are like such, because that is the nature of those programs and not because there is something wrong with Windows XP, some programs are just slow and resource hogs, after all, I am running a 32 bits version of Win XP and it is 2.33 Gigaherts with only 3072 MB of memory RAM and it is a Duo CPU E6550 not great for today's standards.
But I suspect that my computer works much better than many newer computers, to me it seems to be almost lightning fast, but I keep it like that.
My very old, very limited and almost antique Win98SE computer was the fastest computer that I have ever seen and used, it was super responsive and very fast or so it most of the time seemed to be.
But I keep the operating systems lite, uncluttered and clean, how many people really do that? Not very many, I mean "very clean", unlike many people I clean them-up to the extreme.
That sometimes breaks things, but you need to break a few eggs to make mayonnaise, in that way I learn what can be done and what should not be done, after all, these are only "working" partitions and they are a dime a dozen to me, that is they are very easy for me to make-up as needed.
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In all my life I had only 3 operating systems: DOS (Commodore 64), Win98SE and WinXP, I liked all 3 o them, but I think that I do like WinXP Professional SP3 the best.
The comments that I read sometimes on the Lottery Post makes me think that people just don't keep their computers (operating systems) in good enough shape.
Well. to each their own.