Computer freezes while booting into Windows

I own a MacBook Pro Retina 15 inch, and have run Windows 7 64-but on it for a very long time through boot camp.

Today, I turned in the laptop, holding the alt key like you do to boot up into windows.

However, when I click on Windows, the screen just freezes and nothing happens

Does anyone have any ideas on how to fix this? I am really rather annoyed and a little worried. I use windows mainly for gaming and have never had an issue like this before in the time that I have run windows with bootcamp.

All support is much appreciated,

Micah