SERIOUS IOS HELP

Okay so my iPhone 5, CDMA is currently running iOS 7 beta. I'm trying to downgrade back to iOS 6.1.4. My phone is in recovery mode and I currently have no way of accessing my phone. I'm using a windows vista machine, and my iTunes screen will let me restore my phone to 6.1.4, which is what I want. But everytime I try, I get this message that the firmware is not compatible ?? Is anyone else having this problem or have any answers? Anything helps. Thanks