Error installing Windows 7 on Boot Camp

Hi,

I’ve attempted several times to install Windows 7 on Boot Camp. I’ve watched videos and read articles on how to do it, but I just cant seem to figure it out. I know how to partition it and everything, but when I go to install Windows, I get the “No Bootable Device” error message. I know to use the option key to get out of it, but how do I install Windows 7 without getting that error? I really need help.

[Extra info: I have a MacBookPro, Windows 7 (32-bit) downloaded from a school website.]