My machine came with Windows 98SE.  It was tolerable, but I got enough blue screens to put me off.  I stumbled upon Windows ME and gave it a go.  It boots noticably faster, and I experience very few blue screens.  With Tweak UI and System Restore Remover I've been able to tweak it quite a bit...for a nontechie.  I like Windows ME.  I guess that makes me an apostate.