A question about Microsoft Office PowerPoint Veiwer 2007- please help!

I am working on my slideshow presentation; I saved my progress so that I could step away for a few moments. I am not trying to edit what’s already been saved, but I don’t think it will allow me to do so. I worked really hard on this, please tell me there is a way for me to edit what’s already been saved! If so, please give step by step instructions so that I can continue working on it.