Big problem here

i got a new external firewire drive to save my audio stuff on to, when i turned on the pc tonight and went to open a recent project i got the message

G:\ is not accessible
the file or directory is corrupted and unreadable

the same message comes up every way i try to get into my external drive.

I dont really want to format the disk but i dont know of any way rounds this.

Does anyone know why this has happened and how i can avoid it in the future and most importantly can it be fixed without reformating

HELP