Martinio can't see his external hard drive on his computer when he boots up. What software can he use to fix it? Leo says first he'll have to be able to see the drive to fix it. If he can't see it, then there's a hardware issue. It's a very expensive proposition to get the data off. DriveSavers will be able to do it, but it's very expensive.
It could also be the external drive enclosure that's gone bad. If he just wants to get the data off, NewerTech has a USB universal drive adapter than he can use to plug into it, power it, and get it to connect to get the data off. They're pretty inexpensive, too.