boot camp installs partion and boots to black screen

I went through the various steps of bootcamp assisant to install windows 7 on my 2012 mac mini.It created a bootable usb and installed the drivers. Then I sucessfully partioned the disc for windows and rebooted to a black screen.... then nothing happened. I rebooted into mac os and I see a bootcamp drive and my usb flash (boot drive). So i tried to boot from the usb manuelly but it does not show up as an avalbile boot drive. What do I do?