I am qualified to respond to these questions, but this will be my sole post. I will try to keep it short and sweet.

As for what they can do to minors, that varies from jurisdiction to jurisdiction. Prosecution of minors is a very gray legal area. But, Just. Stay. Away. It's not worth it.

I did not read the entire thread, but some people on here were giving bad advice. Do. Not. Ever. turn in child porn to the Feds. If you discover child porn you need to let them know the location of it, but not actually give it to them. POSESSING CHILD PORN IS ILLEGAL. By all means, tell them where they can find it, but do not have a whiff of it on you. However, there are many volunteers who turn in locations of child pornography to the police - this is a very good and noble act. Just be really, really careful. People who have turned in tapes of child porn have been busted for posession...digital downloads are the same thing, legally. So point out, but do not touch. Pretend you found a gun on the side of the road. Sure, call the cops - but don't get your fingerprints or DNA on it.

Most, and I emphasize the word most, people get caught by sharing it. It's the same way with illegally obtained music. If you accidentally download child porn, the first thing you need to do is get it out of the shared folder. The second thing you should do is uninstall the file-sharing program (you can reinstall after this is all said and done). Then download an erasing program. Research it to make sure it is what it is. I recommend at least seven passes with a DoD overwriting algorithm. Good erasure programs will have a few options. ERASE the file in question - don't delete it. (Most erasure programs delete and erase at once.)

Once you've erased the file, then go clear all of your history, temporary internet files, cookies, and document history. Then reboot. Then you want to use the erasure program to overwrite ALL of the free space on your hard drives. I would suggest doing this a few times (with different algorithms) - just in case.

At this point you should be good to go. Running a defrag couldn't hurt either. Also make sure you have anti-spyware and anti-virus software up to date and run them weekly. (This should be done anyway.)

At this point, they'd need an electron microscope to get the data off your hard drive, which is way too expensive to use in prosecution for...well, for most things. Even then, them getting data is a maybe, at best.

If you really think the cops are coming and you've done all of this, then you could reformat your hard drive. If you KNOW that there is a warrant out for you (but have not been given an order to preserve data, which is rare), after the re-format you'll want to degausse the hard-drive using electromagnets. Then make the hard drive disappear. At that point you're 99.999999% sure that they won't be able to get anything.

However, sometimes corporations or government organizations are ordered not to destroy data. Obstruction of justice is a serious charge...the chances of that being applied for this reason in a single criminal case is low.

But, for all intents and purposes, clearing out your history and erasing the file, and then all of the free space on your hard drive is the best way to go. You can sleep well and still use your machine again.

However, the best way to do it is just be really selective on what you download. Do not do massive downloads and pay attention to things as they come in. If you catch something, you catch it right away, before it gets shared.

Anyway, be safe, don't search for it, and be moderately paranoid, and you should be ok!