what is this PSO patch file for
 

Phantasy Star Online Super Cheater
http://megagames.com/dc/dc_patches_p.shtml

also, what is this patch for?
PSO Trainer
http://megagames.com/dc/dc_patches_p.shtml

some people used game shark etc with phantasy star online to give themselves infinate health etc, basically chea while playing the game online, you patch your pso iso with those and it turns on the cheats, although i think on there servers they have something to detect if you are using cheats and will ban you