Not speaking from tons of experience, but the only thing that should slow down your computer is fragmetation. Just having a lot of porn movies on your HD shouldn't do anything, but it is always a good thing to do some cleanup now and again.
My signature was too long so I got this pretty rainbow here instead now. Isn't it nice? This is a nice rainbow.

Risk did this to me and I hate him forever, please join the official "Fuck Risk in the Ass With a Live Bat" social group to join me in hating Risk:
Click here to join my cult to fuck Risk in the ass with a live bat