XP still working well
Like so many others, having invested extensively in software and hardware compatible with Windows XP, I still run a desktop and laptop with the system in place. Neither machine connects to the internet. It works well with the last useful incarnation of Office (2003) before the ribbon made selections harder to find, along with various TV tuner cards and software. My desktop had the network card on the motherboard nobbled during a lightning storm but the rest of the rig runs smoothly. I even went to the extreme of swapping out the original E6750 CPU for a hacked Xeon L5430.
I saw the writing on the wall in terms of internet safety and have gone down the Linux path.
XP was the pinnacle, as far as I am concerned. Windows is trying to be just a little bit too clever and providing functionality no one asked for, wanted or actually benefits from. Linux has my vote from now on and I hope it grows in popularity.