My new usb portable hard drive asking me to format after virus attack. is there any way to get the data back?

i just bought a transcend store jet 320 GB portable hard drive. i store lots of movies and important files in it and i don't have any backup of it. after connecting one of my friends computer ( which was full of virus & have no anti virus too) it begins to ask me to reformat. without formatting the hard drive, it is not opening. what should i do to get all the data back. please help me