Can't see or access my second hard drive

Hi,
I can't see or access my second hard drive. Although it is shown at the start-up screen and also at the disk management window.
It is shown as an unallocated area and i can't initialize it or do anything to it However i can't and i don't want to format this hard drive because it contains a very important data for me

( when i try to initialize the HDD through the disk management it keeps showing an error saying " the request could not be performed because of an I/O device error" )

--More Information--
operating system: Windows 7 pro 64x bit
first hard drive: 1T Western Digital
second hard drive: 1T Western Digital - one partition only