Bootcamp doesn't show up on startup, but shows up in startup disks in system preferences

Hey, I have an iMac 21.5-inch, Mid 2010 running Mac OS 10.11 El Capitan Beta. I just installed windows on my bootcamp partition. I didn't install it through the DVD at boot after the partition was created because my superdrive is broken. So, I have just been booting up with the option/alt key and selecting the Macintosh HD drive to boot from. Otherwise it goes into a screen that says "no bootable disk- Insert boot disk and press any key". I installed windows on the partition by creating a Virtualbox Virtual Machine of Windows 7 Professional, and cloning the image onto the bootcamp partiton (as showed step-by-step in this article- http://huguesval.com/blog/2012/02/installing-windows-7-on-a-mac-without-superdri ve-with-virtualbox/ ). Now i'm trying to boot into windows from my bootcamp partition and it's not showing up in the boot menu at startup. However, if you go to system preferences and startup disks, it shows windows as a startup disk. I have selected windows as the main startup disk but it goes into the no boot disk screen before it boots windows. Is there any way to fix this without deleting my bootcamp partition?