[ubuntu] Mactel single-boot, need to move to Windows

I have a Mac Mini (6,1), which I single-booted to Saucy a number of months ago, and recently updated to Trusty. In the time since I did this, my needs for the computer have changed, and I'm needing to run Windows 7 on it. The problem I'm ruing into is that I can't seem to boot from my USB DVD...