No passwords has no use, they will see EVERYTHING.
And they will check all your porn, they will see what kind of you like too etc....
Well i can't let to much go about the content on my computer because my moms bf reads pretty much everyday the forum here (not sure if he reads general too though)
But i would feel really weird, i'm 100% sure they know i got porn, but i think they will look very strange of the amount lmfao.
Although my father is a dirty asshole, he was even viewing porn on his computer while my mom was around and she never liked it, didn't stopped him though... not to forget he even copied his stuff for my grandfather (my moms dad)
He is a twisted person though... im glad they are not together anymore.