Is there data after January 6th?

The WIn32.Klez.E Question.

I have a client that was “wiped out” by the Klez. They call me on January 7th and said their machine would not boot. After way to long I discovered Klez was the problem and all of their files had been overwritten.
Question: Is there no hope? Does the virus overwrite the whole file or just the header? They are desperate. There are many irreplaceable documents and data files on the drive. Please no preaching to the choir. But some good info, or where to find it, would be greatly appreciated .