[Joeri]

I ran an NT4 / 98 dual boot system for years, and in practice the only applications that required rebooting into 98 were games and things that had a hardware component (scanner, digitizer, ...). So in my recollection the transition was actually quite smooth, games left aside.

[scholia]

One of the things that didn't run on NT4 was the AOL client, which was a pretty big thing for consumers at that time.