When I really think of myself as "getting into programming big time" was my first year of college. I would have been 18 then. I took a couple of programming classes as electives, and "the bug bit" as they say, and I bought the parts to build a PC (386DX40 FTW!) and downloaded a shareware C compiler from a BBS, bought Herbert Schildt's book Teach Yourself C and just dove in... never looked back. :-)
I'm 32.
A few years later, I got interested in game and graphics programming, I started to like it since then.