How can I make my computer private?

K, first, let me say I've never been laughed harder. So, my mother decides to snoop around on my computer (I usually leave it at the sign on screen, with a password) but I've been lazy lately and let a bunch of porn pile up on my desktop, and well, she found them etc but is too embarrassed to talk to me about it. My step-father told me he doesn't care anyways. I feel pretty violated, but who wouldn't? I made a dumbass mistake, and she was being a snooping bitch/ "good parent". ANYWAYS, I'm not computer illiterate, per se. Though, I've never messed around with the tech of it, ms dos, system files etc. I just use it for games, internet, chat, porn, etc. I've been told, by my mother, that she can go in and bypass the sign in screen with safe mode. I haven't tried it, never needed to. Butttt, if that's possible, she could get in no matter what I do, amirite? Is there anyway I can crypt my files/computer so that it needs several sign ins/ inability to access through safe mode, etc? I'm prepared to be wangslapped for my stupidity, but some tips would be appreciated as well.

>>3

I'm not the OP, but this doesn't make a difference. I buy alot of used computers, or am given computers to fix, and if they can't get aroudn a pass, all you do is press (I think) f12 or whatever when it's starting up, and safe mode opens it without a pass word needed. Done it on XP a ton of times.