It's 6 years old or maybe almost 7. I can't even remember if it was late '01 or early '02 when I got it. It's a 1.5 ghz athlon with 256mb ram and it's creaking at the seams. The only thing that discourages me is the thought of having to reinstall eeeeevery fuckin thin. Including some stuff I'm not sure if I even have the install discs for any more. And shit downloaded off the net. Shit that I'll have forgotten I have until I want to use it some time. I'll probably get one one of these days though. One of these dual core or quad core lumps. I don't want windows Fist-ass though, I've heard enough crud about that.. but can you even get an original copy of XP any more?
Your old computer could probably be helped by a good format, yeah you would still have to reinstall everything. Computers, even ones you "take care" of slowly over time build up crap in the registry, file fragmentation, etc... As for porn, I recommend an external hard drive for that, that way it's portable and you can even encrypt the drive to keep prying eyes out.