I don't have RE5, but it depends if it's a "you have one save" game(Like COD, Metro2033, if you start a new game your save is wiped) or if it's a multiple-save game(like BethRPG's, STALKER). If it's the latter, navigate to the game's folder which should be Program Files/Steam/steamapps/(username)/common/ResidentEvil5 (this may not be named ResidentEvil5) but then he should find his save game folder somewhere in there, and could replace his current one with it. If it's the first option however, he's pretty much screwed. If the game has Steam Cloud see if you can revert to a prior cloud-save.