I learned a lot through good old-fashioned experience. I got my very first computer when I was 4 (it was an older model; 1988 maybe?). Being only 4 and never having used a computer (except to play Frogger at a friend's house), I knew nothing about it. All I knew was that it took big funny-looking B-drive disks. Funny, I actually managed to find quite a few games in that format at yard sales. Anyway...the computer only had MS-DOS. It was a bit confusing at first, but I had an MS-DOS For Dummies book that I would read now and then, I believe. After using it long enough, it was second nature. One day, my grandpa brought over an old version of Windows on floppy disks, but the GUI was so foreign to me, I got confused and only used it for a total of maybe two hours.
That really has nothing to do with the question, though; I just felt like sharing a little story. Since then, I have owned four other PC's and each one has taught me different valuable things. Unfortunately, my solution to a lot of major problems was reformatting. But as time went on, I learned to fix more and more problems. When Google came along, this became much easier and I was able to fix even more problems. Then one day, I decided to join Computer Hope and like Calum, I learned vast amounts of information from some of the members here.
Before coming here, I had never slaved a hard drive. Heck, I had never done anything inside of a computer, nor had I even thought of doing so. Now I can do it with my eyes closed. It's funny when I look back because I used to think it was so hard. Back then, the main thing that kept me from upgrading my computer(s) was the steep installation fee. I wish I would've known how easy it is at the time! Several years ago, I actually thought that if I wanted more space, I was going to have to have some soldering experience.
Of course, my area of experience had always been software. I wasn't as dumb as I sound; I just knew very little about the hardware of a computer. Anyway, the point is: everything I have learned has been from experience (anything I help with is likely a problem I have personally dealt with) and this forum. I've still got a lot left to learn, though, of course.