Salvaged possible wallet from corrupt HDD ... now what?
Install Python 2.7 and download pywallet to your c:\ drive. 
Copy your corrupt wallet.dat file to c:\ 
Open a Command Prompt and type:

C:\&gt;pywallet.py --dumpwallet --datadir c:\  --wallet=wallet.dat --recover --recov_device=c:\wallet.dat --recov_size=416Gio --recov_outputdir=c:\


It should extract all the keys to a new wallet on c:\ 
Copy the new wallet.dat to the c:\users\USERNAME\Appdata\Roaming\Bitcoin folder 
rename it wallet.dat. 
Start up Bitcoin-QT with the --rescan switch. 
It should take a while, but eventually it will start up and your coins are back.