XP, the best workhorse Gates ever built !
I finally retired my Gateway lappy w/Win7 on it, matter of fact, my last desktop build with Win 7 is in a box as well.
I built this machine and put it online in January last year, it has Win 10 and is nagging me to go to 11 !
To be honest I hated Windows XP. At the time I clung to Windows 98SE as I knew it in and out and XP was just slow, bloated, took forever to boot up, and always NAGGED the heck out of you (bubble notifications about EVERYTHING). It also ditched real-mode DOS and I still had games that needed it. The Luna UI was the worst form of early skeuomorphism ever done, enough to look like something Fisher-Price made. For those reasons, I stuck with Win98SE until late 2011 when SSL basically obsoleted its ability to use it online.
By then, Vista and Windows 7 were a thing and had a much nicer UI design and Windows 98 finally got put into my history books.
Just to compare:
Bootup times:
Dell Latitude D531 w/ 1GB RAM, AMD Athlon 64 Dual-Core running Windows XP Home Edition "unofficial SP4" with POSReady updates: 35 minutes! Seriously!
Dell Vostro 1700 with 4GB RAM, Core2Duo CPU running Windows 7 Professional x64 SP1: 10 minutes.
Both 2007 laptops. XP still bloated, slow, and ugly. Albeit better with the higher resolution of the D531 and a properly scaled desktop wallpaper. Still nags about everything though, from updates, to security (solved with AVG Antivirus), low virtual memory, HDD space, desktop icons, start menu items, the works. XP still sucks but trying to make that laptop run Windows 7 with 1GB RAM would be worse.