iPod 3rd Gen

i recently found my old iPod 3rd generation (the one with the four buttons on the top and the click wheel) i plug it into my computers firewire port and it starts up. then a folder icon with a "!" shows up i know that means that it cant find the software but i do not know how to restore it. It does not show up in iTunes and the iPod keeps saying its in Disk /mode even though i try to take it out of Disk Mode... Please Help!!!