I'm 14 years old right now, and I have been playing with computers since I was 3.
The media specialist/network administrator at my local school district has hired me as an aide for her during my 4th period and during that time I'm usually out in my school fixing teacher's computers, helping students with computer issues, and sometimes when our school's server is down for whatever reason, I'm usually working on that as well. I know enough about computers that she (the media specialist/network administrator) has given me the administrator credentials to the whole network in case anything I'm working on requires it.
I know PHP, HTML, C, C++, C#, Java, and other languages as well, and I use them often.
I currently administer my own server here at my house. I've setup our Internet connection, our wireless connection, I maintain ALL of our computers at my house.
I'd say I know a lot about computers, but not everything.