Which did you hate most.
Windows 98 for me due to its networking 'capabilities'
http://mashable.com/2012/10/24/windows-startup-sounds/#wO9q4H49cGA
3.1 without doubt. There was the brave new world for those of us who knew mainframe networks, acorns, amstrads and so on with umpteen other operating systems then along came Windows with this grating, irritating start up that sounded like the Tardis due for a serious service. Then it went down every few minuts, jammed and worse, it hung around unimproved for several years with no online updates on early versions because connections were as rare as hens' teeth.