My first OS has to be Windows 98. It was a self assembled computer and it costed my parents about 45,000 INR. They made around 20K INR combined at that point of time, but my father was crazy about the personal computer and he was saving for a long long time to get one.
While my father dabbled with some C++ on it, the only thing I did was play Roadrash and Dave and browse the internet from time to time. Can't believe 19 years has passed already since the release of one of the world's best Operating Systems. Of course, my father tried dual booting the computer by installing Microsoft Windows 2000 Professional for reasons best known to himself.
A few years passed and then came XP. :D Just when you had thought 98 couldn't be bettered, MS amazed the world with XP. It's been a long time since I used a Windows computer, but I think I am indebted to Bill Gates and Microsoft for placing a computer in every kid's room in the 90s.