[abi900]

Recently my computer has been running very slow. I haven't recently downloaded or installed anything, it was just all of a sudden.
I ran AVG and disk defragmenter but it did not help. I have 2 hard drives. C drive which has the operating system installed on it and D drive that has all my files (music, photos, video).
Whenever I tried to open D drive it took almost a minute for it to open and it was the same for every folder on the drive.
This was happening for the last 3 or 4 days and then just before I tried to open D drive and got the error telling me that the drive wasn't formatted and asked me if i wanted to format it. I clicked no as I didn't want to lose my files by formatting and restarted the pc and now it's not showing at all in 'my computer'.
I checked the device manager and disk management and it's not showing up on that either
How can I get my computer to recognise the drive again without losing my files?
Computer is running Windows

Just got a error message saying,
Windows - Corrupt File
Exception processing message.



After some more research, I think my hard drive has died. If so, is there any way I can recover files off a dead hard drive?