Windows 7: How to get data back in my external disk that can't be access?

Hi, i'm from malaysia
I have external hard disk. 500GB Seagate Free Agent GoFlex. It works fine from August 2011 till last Thus (5 July 2012).It appear in my computer as Local Disk(S and appear in disk manager as Raw.
I try with different usb cable,different port,different laptop and different OS but the problem still the same.It does appear in my computer as local disk but when I click 'OPEN' there is a message stated " it is not accessible because of I/O device error". I have assign with new path and letters too but it still the same. The same error message pop up when I want to open it.
I was wondering if there are any ways to access it using software or etc as long as i can get my data in that external disk.I haven't format it yet cause I'm afraid my data will loss forever.There are so many assignments and project data in there and if possible,formatting that cause damage to the data is not my option.Unfortunately for me,I didn't have the backup for data in that external too.
Thank you in advance