Don't Touch My Stuff!

I am a fairly easy going person...if one of the kids needs a dollar or two for school, I'll tell them to look in my wallet and trust them to only take what they need. So far, so good.
Last night, I went to bed before the kids, as we knew they had a late opening for their school because of the snow. However, I knew the livestock would be bellowing, baa-ing, crowing and clucking for their respective breakfasts around 6 a.m. So, I crashed early, after asking the kids to do after dinner clean-up. They said they would, so I took a shower and crawled into bed around 10 p.m.
I get up this morning, feed the animals and come back in the house, grab my camera and go back outside to take a few pics of the lovely snow.
I come in to upload the pictures and discover the cord that connects to my camera has been pulled out of the port on the computer and tossed on the floor. Then I check my computer and find that someone has tried to download something on my computer and my system is now frozen. I wake up my son and he tells me that The Boy was doing something on the computer when he went to bed. My son shuts down and reboots my computer and everything is working...almost.
My camera will no longer upload and a little message tells me on the computer screen that the computer port that the camera cord goes into has experienced a power surge and will no longer work.
The Boy gets up and I ask him---gently---if he was trying to download something after I went to bed.
Immediately he says "She did it, she said it was okay with you, I didn't have nothing to do with it!!!" ("SHE" being his older sister)  His sister, who overheard this, retorts "He was trying to download an album and make copies". The Boy immediately starts screaming more denials, which I have learned, are a positive indication that he is lying. Also, my son saw him at my computer when he got up to get a drink of water.
...sigh...
So, until this issue is fixed, no more pictures.
I have very few items that I outright own. This computer is one of them. I bought it at one of those rent-to-own places and worked very hard to pay it off. It is several years old...I think I got it in 2004. I have taken good care of it, had memory added about 3 years ago and it has moved all over with me. I love this computer.
When I moved here and set up my computer (so we could have a home phone via MagicJack), I took the kids aside and told them to not touch my computer.
Ever.
They have a computer to check emails/facebook/youtube/etc on. I told them if they wanted to watch a movie on my computer, to ask me first! My computer has several idiosyncrasies that only I know how to handle.
Don't touch my stuff.
Simple rule.
Apparently not simple enough for The Boy.
So, yes, I am angry beyond belief. The Boy is 16. A young man who should be showing some signs of responsibility and adult reasoning.
I will be asking my Darlin' Man to help me get my computer fixed and I am sure he will.
I don't know what to do about The Boy. This is not his first lie. He lies constantly and then tries to "suck up" when his lies are discovered or to lay the blame on someone else. He attempts to manipulate every adult around him to his advantage. He can be very charming...but I am afraid that is part of the problem. Some adults believe his B.S.
I had kids before. Saw them through their teens. Had a couple that tried to get lies past me...which rarely worked. I was kid once, too!
So...I have some decisions to make before The Boy gets home from school today.