Salvaging slides from corrupted file

I am new and need some advice.

Was working on my file yesterday and *thought* I was deleting one Master Slide (but somehow deleted all of them).  Today the file appears corrupted and won't open. 

I do have a backup file from a week ago, but I want to know if there is any way to salvage anything out of my corrupted files.  I had just created some great slides (with layers, sounds, graphics,  and animations) and I'm not sure if I remember how I got them to work.

Thanks,

Gillian

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