The only old game I've played recently is SWOS, although I did lose hours and hours to it this year.
I could go on for hours about old games. I could list enough stuff that you could get for free with easy ways to play it to keep anybody going for a few years. It's not only old games, but the current crop of freeware games and remakes fuelled by the internet are fucking brilliant.
I could list stuff but I won't. Not until I get so overwhelmed with geekiness to start a free(or nearly) stuff you can do with your shitty old computer thread anyway.