Serious Trouble!!!

I am a music recorder and i have a western digital external hard drive. I have music files on my computer that are not showing up now, after i added my latest song to my hard drive. I have over 100 songs in this hard drive. The driver was titled Blokwatch, but now when i plug it up, all it is saying is "Local Disk (E:)." Nothing is showing up, and i can't open any existing files. I really need someones help, because my life is on this hard drive. When i click on the drive, it keeps saying that i need to format the disk, but i was using the hard drive previously, and this problem never accurd. Can someone please help me