I'm sorry to hear of your loss of data.
I'm also sorry to have to say that people can almost never recover damaged PSD files. This is one reason Photoshop CS6 is coming out with an Auto Save function.
Did you save your master file in several different locations, or do you have a backup? Make sure you protect any backed-up files ASAP, before they're overwritten by the corrupted one.
What do you see when you right-click the PSD file, and choose Previous Versions (assuming you have Vista or Win7)?
Under some conditions there's a possibility of recovering a flattened version from a truncated PSD file, depending on how you have your settings (maximize compatibility causes a flattened preview to be saved at the front of the file).
When I right click it says there are no previous versions available. When you back up..do you just mean like backed up on a cd I can throw in the pc? I didn`t make copied files and save them. It is windows 7 also.