I don't have to worry, I'm the youngest in my family and my parents are computer illiterate. I don't worry about my brother using mine cause he has his own which is slightly better than mine, dad does use mine in the morning which pisses me off, cause he 'has to' always go to look on the weather sites, but he doesn't know how to do that so I had to put the weather sites as shortcuts on the desktop >_>;.
I would password protect my computer but then my dad would rip out the internet because he 'pays for the bills and has say over everything', I would create another user just for 'other people' to use, but then windows wouldn't log on straight away (which I really like cause I turn the comp on, go to the toilet and when I'm back it's fully loaded).
But if I did password it I would have 'beaver'.