I too got it the same way by trial and error. My desktop is assembled one. So the retailer gives 1 year warranty i.e, service free. So in that one year I have done a lot of experiments. I have got my hard disk replaced once. My dvd writer was broken so I opened it completely to see its working mechanism. I have changed my SMPS two times (it was due to voltage problem) so opened the faulty one too. And saw the what is in it. Had an old hard drive of 6 GB which was not working opened that too and got how hard disks store data. Have broken my CPU fan myself. Replaced it.
And in the software you are free to do anything as how big the problem be mostly a clean install of the os repairs it.
Still learning don't know so much of computers. And reading threads in the forum helps a lot too. And also can ask my doubts freely to the experts here. This forum is awesome. And thanks to all the members for helping us.