Bootcamp problem after upgrading to Yosemite (disk0s4)

I used to have Bootcamp running Windows 7. Then i did the upgrade to Yosemite and all the sudden I don't find it in the Startup Manager anymore. Then I looked it up in Disk Utility and it comes as "disk0s4" in gray. I used several Microsoft software for college, and now i don't know what to do. How can I recover my Bootcamp again, or is that even possible?

Thanks for your help! I'm new in the scene.