Formatting Portable Hardrive

A friend of mine has a portable hardrive, last week he dropped it its been working fine until he went to format it, today. It doesnt sound like there has been any physical damage to it though as he can still take files from it and add to it, but he wants to format it.

Trying from cmd propt says its not a recognisable file system.

Trying through windows says windows could not complete the format

And he also said he's tried disk manager too but that wont finish.

Anyone any ideas on what to use or how he might be able to format it?

Thanks :)