I need help to get my 320 gig external opened

I bought a 320 gig external for my Dad last year for his b-day. I basically filled up for him. Well when he took it home and tried to use it, he said the thing wouldn’t pull up all the movies that I put on there. I don’t know how he messed it up in one day… But he did. I am wondering when I plug it into my computer it shows under hard disk drives local disk E: but then when I try to click on it a error message comes up saying my windows explorer isn’t working and shuts it down.Please if anyone can help to just reset it or anything that would be great.