Time for a defrag

really? Surely it'd just slow down disk access a lot, not actually crash it?
You bet. If your drive gets too fragmented it'll eventually make your file allocation table unreadable. It happens more then people think cus most of the computers it happens to are old, owned by a person who uses the crap out of it, and never been defragged. So when ppl see the missing ntfs and fat32 errors they just assume the hdd is too old and having hardware issues instead of popping it in another machine and attempting to mount and defrag it which shockingly usually fixes the problem. Although it takes about 5-10 very long defrags to get it done.