Data Recovery

What is the best route for data that is lost?

When I say lost, I don't mean that I deleted it. I had a system crash, and a couple days later I was getting errors when copying to the LaCie Bigger disk. Now the drive only sees 1.2GB when there is over 400GB of data on it. It is a 1TB drive. How should I proceed?

What is weird, is that when I look at the properties of the drive, it says that 445GB is used, which seems normal, but when I browse the disk, there is only a couple folders and they add up to about 1.2GB. Help!

 

Bump.