Wolvix is a desktop oriented GNU/Linux distribution based on Slackware. It features the Xfce desktop environment and a comprehensive selection of development, graphics, multimedia, network and office applications. It's mainly targeted at home users and strives to provide a balance between everyday computing tasks, creativity, work and enjoyment.
Though Wolvix is fast and has a low memory footprint, it's not specifically developed for old computers, as it features modern software; which has modern hardware requirements. But it should perform well on systems which are not the latest and greatest. You should get acceptable performance from Wolvix and most of it's applications on a computer with a 700Mhz CPU and 256MB RAM.