Truecrypt-Permanently decrypting external HDD stuck

Hello! I have a 1TB external HDD crypted with TrueCrypt since a couple of months and it's 99% full of important files. I wanted to decrypt it so I used "permanent decrypt", put my password and the progress bar is at 0.029% and the estimating time got from 8 hours to 160 days and counting and then I head a short and high pitched noise from my external hdd and I get an error (the device isn't ready) and after clicking ok I get another error (In the picture) and then stops. This repeats when I always try to resume the decrypting process.
I'm using a Windows 8 Live CD as my internal hard drive it's almost dead as well, looking to recover some stuff with testdisk..
Since it's such a small percent, can I restore volume header to make it work again? What do you suggest?