Being in my 40's, there was no such diagnosis as Aspergers when I was growing up. (Damn, that sounded old...) I just had notations on my report cards like, "likes to play alone, not very social." and "does not apply himself. He's very smart, but just doesn't try." Looking back on it now, had I been growing up now, the teachers would have immediately realized I had ADD first off, then most likely would have recognized Aspergers. I didn't have friends growing up, I was the kid that everyone could get to do the stupidest things because I just didn't realize they weren't being serious. I was VERY rules oriented, it made me crazy when someone didn't follow the rules. (Still does, but I've learned to adapt.)
What made the light bulb go on for me was first watching TLC's show about people with exceptional talents. They featured a guy with Aspergers who had no friends and no social life, but could design electronic circuits in his head. A lot of what he was talking about resonated with me. That planted the seeds. Then, I was talking with an on-line friend who had just been diagnosed and he pointed me to one of the on-line assessments for Aspergers. I tried it for a lark and was shocked when I scored VERY high on their scale. I took another test and got the same results. So, I started doing research on Aspergers and finally spoke with a psychiatrist through my work and got a confiming diagnosis from him. The thing that irritated me about that though was what he kept telling me, "What does it matter?" It does matter. It affects my life and my relationships.