I tried installing it on my 20mhz 486 IBM but the install never would finish even though the minimum specs listed 386. I always thought that was being too generous. I did use it on faster 486's at some point in school (I think 66mhz or faster?)

Yup, the RAM was the main bottleneck. 8MB was the minimum for Win9x, 16MB and above led to a fast experience.