loved, loved, loved desqview. and qemm. https://en.wikipedia.org/wiki/QEMM

it was largely eliminated by windows 3.1 but before win3.1 it was the best way to run multiple apps at same time. the ability to devote a % of the cpu to various apps so that your word processor barely ticked over in the background while your spreadsheet was working away happily was wonderful on the limited pcs of the time.