For me it was around 1995. I had a new computer on order, a 166 mhz pentium to replace my old IBM PC XT and I was browsing the O'reilly books in a bookstore and came across a book called "Running Linux". I started reading it and I found it interesting. A multitasking, multiuser Unix-like clone. It reminded me of the systems I used in academia. It came with 2 discs. So, I bought it. When I got my new Pentium I partitioned the 2 Gb Windows drive and installed Linux. It was an early 1.x kernel. It was crude, primitive, needed a lot of recompilation and reconfigs and it was nerdy/geeky as hell. But I liked it better than Windows 95. I've been using it ever since and loving it even more these days.