How did you break a computer by tinkering? If you tell me that you screwed up a Windows installation, you know you can reinstall it, right? If I had a dollar for every person who thinks their computer is irreparably damaged solely because Windows no longer boots up, I'd be a very rich man.
You sound like you might be into this stuff. Get yourself some basic electronics knowledge.
http://www.gamesx.com is a great place to start for gaming hardware and some electronics theory.
http://www.pinouts.ru for pinouts of just about anything. Those sites are great for reference. Get your parents to get you some books about the basics. I don't have any to recommend, unfortunately. I'm a bit past that.
Get some soldering equipment. Radio Shack's not bad for beginners, but I'd recommend some quality Hakko equipment from
http://www.techni-tool.com when or if you feel you've graduated to the next level.
Want to reinstall Windows? Google around. If you've at the very least got a CD key license sticker on the computer, you can probably reinstall a legit Windows even if you don't currently have an installer CD. It's not rocket science. I figured out aspects of it for myself, and if you screw up, you can always start over. When it comes to installing Windows, the only thing you've got to waste is time. Don't fear the BIOS either. Treat it with respect, and it won't let you down.