Uh oh, looks like you've let the cat out of the bag. I almost got caught too; I had JWD onscreen, not minimized. Thankfully nothing came of it (yet...).
Well, judging by your folks reactions, they are quite disturbed to find this material of yours. Since an apostate is worse than Satan according to the WTS, they are feeling emotionally devastated. Try not to do anything to exacerbate the problem by being brusque with them. As I see it, you have a couple ways this accident can play out: you can be defensive over the issue and trigger a fallout with your parents and a quick JC, or you can try your darndest to play the "I needed to investigate some claims" defense. Neither path is desirable, and you should assume that shit is going to get ugly right away.
When you are confronted about your material, you will be asked what could possibly lead you to look at this stuff. There are a number of explanations you could give, but you need to tie in some part about an outsider (like a forum member or myspace friend) making claims about JWs. I don't know what subjects you were looking at in particular, but it's probably safe to say that you could talk about the UN DPI scandal, for one. Remember, you need to mention something that hasn't been covered in the literature. You needed to go on the internet to find out about something the Society hasn't addressed.
Here's some answers you could have ready:
Them: "Son, you know these are apostate lies about _______! There's no way you could even think about looking at them."
You: "I'm sorry, but I needed to answer _____ about this issue with the best evidence I could find. The literature doesn't talk about it. I would've gone to the CD right away, but the Society didn't have any information about _____. I was confident that what I would find would reveal the truth about the matter. Besides, if the Society's done nothing wrong, then there's no reason to be afraid to search for the answers.
Them: "There's no point in searching the internet for information on the Society. It's all negative. If it doesn't come from the Society, you know it's an apostate lie!"
You: "I was worried about that. But the information I found out came from third-party sources who have no reason to malign the Witnesses. If an encyclopedia states (that Jerusalem was destroyed in 587 BCE, etc.), then how is that some sort of apostate campaign? Don't I have some reason to be concerned if authoritative historical sources have one claim, and we have another? Aren't we supposed to make sure of all things? Besides, not considering someone's viewpoint just because you don't like them wouldn't hold up in a court of law. It's a logical fallacy to attack the person and not their argument, and I wanted to make sure I went about this whole thing logically."
Them: "Don't you believe in the Slave? Are you doubting God's Channel?"
You: "Look, you know I love the friends, and I love going to the meetings. But how can I defend the Truth if I'm not even informed about the same things that they are? You know, that's what _____ said about the Witnesses. He said our organization was a high control group because it's members weren't allowed to research it's past history. That really hurt. I needed to prove him wrong, and so I started doing research outside of the Society's literature."
Them: "You know that communicating with apostates/disfellowed persons will only lead to spiritual shipwreck. Why did you even get started down that road?"
You: "The Apostle Paul talked about building with fire-resistant materials. That's how I hope my faith has been built. He was willing to defend the resurrection and his faith with the staunchest of opposers. Peter did the same. The point is that there is a Biblical precedent to defending our faith with unbelievers. I was encouraged by their examples most of all. Besides, I was talking with people who hadn't been disfellowshipped."
Them: "But son, all the material we found was critical of the Watchtower Society."
You: "I needed to weigh their evidence against ours. Believe me, I have our arguments well in mind, and they do stack up against theirs in a number of ways (give an example)."
There's about a snowball's chance in hell that you will get off, but it's worth it to try and calm them down. The status quo has been ruined, and you should think about them kicking you out of the house, and you being df'd. Consider all your plans to make a painless exit scrapped. By preparing for war, you can best hope to survive this critical situation.