As someone who manages a fleet of 30 windows machines that house PCI DAQ cards: Windows 10 runs on a Pentium 4, but I wouldn't call it fine. All of the machines run on SSDs, which is a godsend, but the older machines that run pentiums involve a lot of waiting around to do the most basic of things. It doesn't help that Windows refuses to us less than 1.5 GB of RAM. You can forget web browsing.
I gave them Lubuntu and their scanner app running in WINE.
It worked fine but they refused to switch because "it's not muh windows". This is how Microsoft corrupts people for life...
The sad irony being that the Windows UI, starting from Win8, became a complete mess, far more different from say Win7 or even XP than any recent Linux desktop manager.
Most of my users, some even over 70 with little computer experience, are doing fine on Linux, but I "converted" them before they had to experience that awful mess, so it has been relatively easy: from XP or Win7 to a customized XFCE (its defaults are ugly and unpractical) has been a breeze.
