Error renaming protected PowerPoint file

Hello all. I have a PowerPoint file which I saved as file protected. Right now, I wanted to rename it but it just happened that after renaming, it won’t accept my password at all. How can I rename this file? So I could not access it anymore and I would need to work with this huge presentation I have. I don’t want to do them again so please help me get through this problem. I’m using MS Office 2010. Thanks!
