Windows NT 4.0 existed at the same time with the same UI and without the instability. Effortless MP3 playback was primarily made possible by hardware advances, not software ones.
From my memories NT branch was unstable until at least XP SP2. Not sure if it was because of the OS itself, or because most of the software and drivers were written for Windows 98, and required few years to catch up.
Windows NT was rock solid until Windows XP was released, but GPU performance was meh and Windows games generally didn't work well unless they were written to target NT. As I recall, there was one commercial graphical strategy game for NT at the time.
XP broke the subsystem isolation of NT in favor of enabling Windows non-NT types of drivers with higher levels of kernel/GPU efficiency due to less isolation. This also brought in the ability of the drivers to crash the kernel.
And that, my friends, was the end of rock solid Windows NT stability.
I was on the Windows team during the XP SP2 years. Stability was somewhat reachieved by an intense focus on defensive coding to detect rogue driver and the establishment of the WHQL, or Windows Hardware Quality Lab. WHQL was basically an investment in driver analysis tools and a moderately sized team inside MSFT who's sole job was to debug and fix other people's drivers.
It's not a good replacement for isolation though, and it requires sustained continuous effort by both MSFT and the windows hardware partners, which imho hasn't continued.
