In 2002 after spending my first 30 minutes on windows XP (previously 98, 95 and 3.11 user) I realized that Microsoft will never improve their UX. Every new os will be different, but not better. So I left then and there and never looked back, after some distro tourism I settled on Ubuntu in 2006 and use it even now.

It was getting better until they integrated IE in Win98.