you have to use a media server from your pc and set up your ps3 on your home network to allow file sharing . look on the ps3 network settings menu to enable it .
ps3 only supports one divx format ( there are several versions ) so you might need a media server that can convert and stream in a usable format or to convert the files yourself if you use wmp11 as your server .
check your ps3 manual for setup instructions and on your pc for how to enable file sharing and select the files .